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Am Ind Hyg Assoc. J 43(8) 605-621 (1982) The history of development and validation testing of passive dosimeters is reviewed. Theoretical considerations, including possible limiting factors or interferences, are presented. Laboratory and field validation tests are critically reviewed and results are presented for comparative purposes. Evaluation of available data indicates that passive dosimetry, with some exceptions, is an acceptable method for monitoring gasses and vapors. Most importantly, passive systems appear to be as reliable as the now accepted active sampling systems. Passive dosimetry -- state of the art review VERNONE ROSE and JIMMY L PERKINS School of Public Health. University of Alabama in Birmingham, Birmingham. AL 35294 introduction ccognition. evaluation and control are the cornerstones of the application of that mixture ol science and art known as industrial hygiene. These three tasks, how ever, a re no longer the eminent domain of the industrial hygienist. In the past decade, a proliferation of training in the recognition of workplace hazards has been made widely available to workers and management alike. At the other end of the spectrum has been the tiaining of indiv iduals highly special ised in the control of specific hazards. especially those inv olv ing noise and toxic air contaminants These develop ments are welcomed because they contribute significantly to the ultimate goal of protecting the health of workers by providing safer and more healthful workplaces. At the same time, professional industrial hygienists rec ognize that often the critical step in the process is not recog nition of toxicity, but evaluation of hazard which leads to the subsequent development of the most effective means of control where warranted. This key step of evaluation is the unique domain of the industrial hygienist. often supple mented bv other members of the occupational health and safety team. Where evaluation requires thedetermination of worker exposure to airborne toxic substances, the industrial hygienist has seen a revolution in the development of sophis ticated techniques and equipment. The "organ-grinder" impingcr sampler is a relic, having been replaced by constant flow , eight-hour battery-operated pumps, light enough to be carried by the worker. The liquid bubbler and impingcr have been replaced by the charcoal and chemical substrate sampling tube. The laboratory has come to the field in the form of the portable gas chromato graph and infrared monitor, albeit with a price rise directly proportional to the sophistication of the equipment. Even the once lowly, direct-reading detector tube has become legitimate with the establishment of government programs to certify accuracy and precision. But while most evaluation techniques were reaching the point w here the industrial hygiene staff required the addition of someone with a Ph.D. in electrical engineering, a new device has appeared which has the key of simplicity -- the Copvr*9*t 1962 AftvMcan Ainsiirin Induvirui Hy(*ne Iswcution JOURNAL (43j f B? personal passivedosimeter: personal, because it can he worn by the worker in close proximity to the breathing zone, passive, because there is no pump to move the air over a collector, which equates to fewer calibration and mainte nance problems. Some quarrel with the term dosimeter, with purists preferring to call them collectors, monitors, or samplers. While many of the devices are collectors and require the application of subsequent analytical procedures, others provide for a more direct measurement ol "exposure dose." Their basic appeal, however, is simplicity of use Theoretically .elaborate calibration procedures a re unneces sary. and all that is needed is a fairly reliable timepiece to measure exposure duration. There is some recognition that temperature and humidity may affect the observations, therefore, most manufacturers advise the user to report these environmental conditions to the analytical laboratory pro cessing the dosimeter. Rather than v iewing passive dosimeters as another way to replace the industrial hygienist, industrial hygienists must recognize and appreciate the potential of the dosimeiers in helping to achieve the hygienists' goals. That potential is significant in that personal dosimeters, if properly used, offer the opportunity to revolutionize the evaluation step. The parallels with detector tubes, as well as with noise and ionizing radiation dosimeters, are obvious. Indeed, the parallel with radiation dosimeters, especially film badges, is striking. The opportunity to significantly expand the mea surement of worker exposure to many toxic material' can provide a quantum leap in our ability to provide sale and healthful workplaces. With any sampling device, however, there also must be the understanding that use ol such dev ices is only one pan of the evaluation step. The concepts of proper selection of workers at risk: the understanding of limitations, interferences and similar factors, and ultimately the proper interpretation of the results afe still key ingre dients in the evaluation step. 1 he possibility ol "lake nega tive*' decisions leading to erroneous assumptions ol salciy. or "false positive" conclusions leading to unwarranted expenditures of resources lor coniioK still exists icgardlcss of the measurement device used. rial Hvgifrw Afirviaticr 3M 001496 With the rapid proliferation of passive dosimeters in the past several years, it is appropriate that industrial hygienists evaluate the "state-of-the-art"and. as professionals, become involved with the proper application of these monitor ing devices. theories of operation In that passive dosimeters by definition do not use an air moving device to transport contaminated air to a collector, natural forces are relied upon to ensure that a representative amount of contaminant is "seen" by the detector. 1 o date, one of two principles has hcen applied in the design of dosimeters. 7he first, and most widely used, isthc principle of diffusion of contaminant molecules through a stagnant pas (air) layer 7 he second principle involves the absorption in and subsequent />i'r>runon ol contaminant molecules through a membrane Ddluuonal monitors rely on the movement ol contami nant molecules across a concentration gradient which for steady-state conditions, can be defined by Kick's First l aw of Diffusion 11 \\ = - DA d--c dv (1) where. W = mass transfer rate, ng see. D = diflusion coefficient, cm' see. A = cross sectional urea of diffusion path. cm*, and dc dv - the instantaneous rate of change in concentra tion over diffusion path, (ng cnvVnt '. Considering the change in concent rat ion (Ci -- Co) over the total dillusion path length (Xi -- X.. = -- l.l. equation (1) heeomes: W = D Y (C, - C,,) (2) where, 1. - length of the diffusion (static! path. cm. Ci = ambient concentration of contaminant, ng cm1, and Co = concentration of contaminant at collecting sur face. ng cm'. II an effective collection medium isemployed.the contam inant concentration at the surface of the collect or (Cn) can be assumed to he rero. and multiply ing both sides of equation (2) by time, y ields: M = D ~ tC,) i (3) where: M -- total mass transferred, ng. and t = time that the badge is exposed to the contami nated air. sec It is also interesting to note that the units of the product of Dand A.divided by l..arecnv' sec. which are the same units associated with active air-moving devices such as personal sampling pumps. Rearranging equation (3) as follows: it becomes apparent that live lactorsalfect the measurement of the ambient air concent rat ion of a substance (C7) 7 wool the lactors (L and A) arc physical parameters associated with the construction of the dosimeter, one (M) is prov ided by measuring the total mass of contaminant collected by the sampler, another is the duration (tithe sampler was ex posed to the contaminated atmosphere, and the final factor (Dman individual property of each vapor or gas. It also o known11' that the diflusion coefficient is directly propmtional to the absolute temperature (T) of the vapor, raised to three-halves power and inversely proportional to the atmo spheric pressure (P). Dn -- (51 Dosimeters that rely on the principle of [htiiuuiioii through a membrane are especially useful w here the contam inant of concern is usually found mixed with other intcrlciing vapors or gases or when a liquid collecting medium is employed. The goal then becomes to identify a membrane material that is highly permcahle to the contaminant ot interest and impermeable to most other components in the atmosphere, and or the collecting media. The determination of ambient concentrations of a con taminant usinga permeation dev ice can be determined Irom the formula: C = wk l (6) where. C = concentration of contaminant, ppm, w = mass ol contaminant collected, qg. k = permeation constant, ppm-hours yig. and t = exposure time, hours. The permeation constant (k) is determined experimentally and is a function of the specific membrane material and contaminant of interest,1'1 sources of measurement error The most obvious sources of error for both types of passive dosimeters are apparent from equations (4) and (6). Com mon to both badges are determinations of the mass of con taminant collected and the time of exposure of the dosimeter to the contaminated atmosphere. For the diffusional moni tor, accurate knowledge of the physical parameters asso ciated with badge construction (length and cross-sectional area) and the diffusion coefficient of ihe contaminant are important. There are at least nine prediction methods for calculating the diffusion coefficient, and in one study com paring observed and expected values for more than 100 compounds it was not uncommon to have less than 50 percent of the calculated results within 5 percent of the observed.1,1 Montalvo has described a procedure for limiting errors associated with computed diffusion coefficients.'*' At 3M 001497tot Am inO Hyf Asioc J(43) August 19&,` least one manufacturer, the 3M Company, makes available its procedures for determining sampling rates (DA, L)for its badges.151 Itsapproach has been tocxperimcntally determine the sampling rate for fisc or six compounds in a chemical family to establish the relationship between the diffusion coefficient and the measured sampling rates. Sampling rates for other compounds are determined from the diffusion coefficients calculated by the Hirschfelder equation and the empirical relationships developed from the lest compounds, f he rationale for the selection of the Hirschfelder equation is not given. but in the study of the nine diffusion coefficient fotmulas, the author concluded that for higher molecular weight compounds the Hirschlelder. Biardand Spat/equa tions were in closest agreement with determined values.'3' Foi the permeation monitor, accurate determination ol the permeation coefficient for each monitor is necessarv for obtaining accurate results. Factors influencing permeation include: thickness and unifoimity ol the membrane, affinity ol the membrane for the ana ly te. swelling or shrinkage of the memhiane, and possible etching by corrosive chemicals. The piohlcms associated w ith accurate determinations of the mass ol the contaminant collected arc similar to those involved with other collection devices such as charcoal or silica gel tubes, or to those in which the collection of the contaminant ins olses a chemical reaction with the collection medium. Using known amounts or concentrations of con taminants to determine collection and or desorption effi ciencies is as critical a step lor passive dosimeters as it is for othet methods ol collection. Saturation of the sorbent as well as the subsequent accuracy ol analytical techniques are also part of the total etror associated w ith the measurement. Another common concern in all types of environmental measurements is the potential for interferences, either posi tive or negative, from other contaminants in the.sampled air. As the evaluation ol passive dosimeters has matured, increased attention is being paid to possible interferences in multi-contaminant exposure situations, in both the labora tory and field. In evaluating such interferences it should be recognized that there are several potential sites for such interferences to appear, c.g.. effects on adsorption or absorption efficiency ol the sampling medium, chemical reactions of two or more contaminants prior to analysis, and the multitude of interferences associated with analvsis of complex mixtures of gases and or vapors. These problems also arc found in the more classical sampling and analvtical methods. Accurate measurement of the time the sampling device is exposed, is essential to most industrial hygiene sampling procedures. For both short-term and full-shift exposure measurements, errors less than one percent, i.e. 9 seconds in 15 minutes and 4.8 minutes over 8 hours, are not unreason able goals. For the diffusion coefficient and possibly the permeation constant, it would appear that three factors have the greatest eflcct on variability. These factors are the two already identi fied. temperature and pressure, and. less readily apparent, the velocity of the air external to the badges. Considering temperature and pressure, and rclcrring to equation (Slit can be shown that a temperature rise from S to 35 C would give a 16 percent increase in the diffusion coefficient, while a rise in barometric pressure from 710 to 810 mm Hg would cause a 14 percent decrease,'1' Howevei. at the same time, the changes in temperature and pressure also are affecting the concentration (mass volume: actually, density is the proper term but most authors use concentra tion) of the contaminant in that concentration is inversely proportional to the temperature and directly proportional to the pressure. Asa result, the total mass(M)collected by the dosimeter is only slightly affected by temperature ( M 1 ' ') and is independent of the pressure."'Consequently. w bile at ambient temperatures, the diffusion coefficient w ill increase about 0.5 percent pcrC.and thetotal mass collected by the sampler will increase less than 0.2 percent per C. There! oie. a temperature change from 25 to 30 C. if uncoirected. will introduce a measurement error of less than one percent, while a change from 5 to 35 C. if uncorrectcd. would introduce an error of about five percent. The final source of erroi to consider is the velocity ol the air external to the dosimeter; often this is referred to as lace velocity. In an early assessment of face velocity effects, espe cially the lack thereof. Tompkins and Goldsmith point out that the important consideration is to contain all resistance to contaminant transport within the stagnant air layer inside the device."' As Jonas ei al. subsequently noted, the face velocity directly aflccts the concentration gradient C'|--Ci. in equation (2). and Ci can no longer be assumed to be the ambient concentration when the air external to the badge is stagnant.'' With zero or low face velocities, the length (I ) ol the diffusion pathway is effectively extended, and there is a decrease in the measured ambient concentration In Tompkins'and Goldsmith's work with the GASBADGFTM. they determined experimentally that as long as lace veloci ties were greater than 7.5 cm sec (15 fpm) there was "no significant effect on dosimeter response:" however, experi mental results supporting this conclusion were not pre sented."' High face velocities may also affect the coneentiation gradient. Commercially available diffusion devices rely on either a large ratio of diffusion path length to diffu sion tube diameter or a wind screen to limit errors from this condition. One of the most comprehensive tests to document sources of error has been conducted under contract for the National Institute for Occupational Safety and Heallh. and although concluded, it is not yet available as a public report,' The study involved evaluation of the GASBAIXif and 3M Organic Vapor MonitorTM (the DuPont badge not being available at the time the study was initialed) via challenge with several organic vapors. The factors investigated were precision, effects of storage, maximum and minimum levels of quantification, face velocity effects, effects of temperature and humidity, off-gassing (related to storage), exposure to mixtures, problems associated with applicable analytical methods, and adsorption of the contaminant by the badge itself with subsequent leaching to the sensing surface. The possibility of adsorption by the badge body, thus giving Am?ricr industrial Hvpienp Association JOURNAL HI) B B? 3H 001498 nghet results if the contaminant is subsequently released to he acti\e medium, is of special concern in using passive losimcters to measure very low ambient concentrations -uch as might be found in air pollution studies. Such interest ind concern are evidenced by research on the subject being sponsored by the U.S. Environmental Protection Agency EPA)ie) Because of the lower concentrations involved with air pollution studies as opposed to workplace environments, the EPA also is concerned with the background or post manufacture contamination levels associated with the sens ing medium. Initially. the focus concerns organics and acti vated charcoal. In summary, although numerous factors may affect the final calculation ol concentration, only face velocity and the determination ol the diflusion coefficient are unique sources of error for passive collectors. Therefore, if face velocities arc sufficient to prevent "starvation"(probably greater than ? 5cm secland if diffusion coefficients have been accurately calculated orexperimcntally determined, passive dosimeters should giv c results comparable to those obtained w ith tradiional active sampling systems. statistical considerations In evaluating any new monitoring method.extensive laboraory and field testing is necessary. Interpretation of the results of these tests requires the application of appropriate statistical techniques. The use of statistical techniques which are meaningful and easily understood is important: conse quently. a discussion of the techniques used to evaluate passive dosimeters is appropriate. There are numerous statistical tests which can be applied o both field and laboratory validation data. The main diference between the two situations is the degree of certainty of the "true" concentration of the monitored environment. In the field, the true value is usually an estimate based on the results of a standard sampling and analytical method. In the laboratory. experimental "know n~concent rations are ev olv ed and are then used for comparison with the concentrations estimated from sampling and analytical methods. What is often not stated is that a certain amount of error also exists in the determination of laboratory-evolved "know n" concentrations. These errors are often difficult to estimate. The "known"concentration is often calculated byweighing a sy ringe before and after an injection period (mass valance) or simply by injecting or allowing to diffuse a neasured volume. It is assumed that the aliquot delivered x as vapori7ed or diffused into a test chamber of know n sire. Possible sources of error include adsorption to or leaks from the test chamber, absorption and adsorption to articles placed in the chamber, degradation of the analyte by air oxidation or hydrolysis at high relative humidities, and error in measuring the injected contaminant. A backup monitor ing system may be used to ensure close proximity to the `know n "concent rat ion. For example, an infta-red (IR)anay/cr or gas chromatograph may be used as a check on a known "concent rat ion. In other instances an IR analyzer or a direct reading instrumeni may bethc only method for determining "known" vo concentrations. In this case the error in the instrument can be calculated or estimated. Charcoal tubes and critical ori fices also have been used to measure "known" concentra tions. If error in both the "known" concentration and the estimated concentration are considered, statistical tests used to validate the experimental method become considerably more complicated; hence, the error in measuring the "know n" concentration is usually assumed to be small and unimpor tant.181 Methods described above for deierminini the "known" concentration vary in their accuracy, a fact which should he considered w-hert evaluating validation data for any sam pling and analytical method. When one is validating a method in the laboratory. there are two main considerations: the variation of the samples or data points about their mean, and the deviation of the sam ple mean from the true mean or "know^"concentration. The first consideration often is called precision and is probabh the most important and reliable measure as it does not depend on the error in determining the "known" concent ra tion. Precision is estimated by determining the coefficient of variation (CV) or relative standard deviation of the data set as follows: CV = ~ X 100 (7) where: s = Standard deviation of sample data set. and X = Mean of sample data set. Where samples arc taken at several concentrations, it is necessary to determine a pooled coefficient of variation which involves determination of number of levels tested.'10' It should be noted that determining the number of concen trations (or more appropriately, the number of statistical levels) is not always straightforward For example, if 10 samples are taken at each of three concentrations, and if within each concentration five of the samples are collected over four hours while the other five are collected over eight hours, are there three levels or six levels? The important point to consider is whether the differentiation of a level is based upon an anticipated difference in the sample mean. Certainly if the investigator designs the experiment with different time levels, there is an anticipated effect of time on the mean. Unfortunately, when experiments are so designed, statistical analyses at the various levels usually are not performed. The second statistical consideration, the difference between the sample mean and the "known" value, is sometimes called accuracy, but the term bias is more appropriate. It is defined as: b = -X~~ X- X IO0 Xo (8) where: X = mean of sample data set, and Xo = "known" value at level tested. If more than one level is sampled, it is necessary to determine the pooled bias of the data set.IUl 3M 001499 Am Ind Hy[ Assoc ) H3 Adjust 198? The bias for a given set of data can sometimes be cor rected. If the average bias (either the average of several samples at one level or the pooled bias for several levels) is large, one should note if the components of the bias value (either the individual samples or the levels)are consistent!) negative or positive. If the bias is large and varies consistenth in one direction, the precision nevertheless may be quite small. In this case a physical or chemical variable may be consistently affecting the method (a systematic as opposed to random error), causing the experimental values to con stantly fall short or long of the"known"concentration. This form of bias should be corrected. In addition to these statistical tests, others have been used to assess the validity of passive monitoring systems. Overall system accuracy11" has been defined as (2 X CV) + absolute bias, expressed as a percent. Others021 have used the percent age of the "Known" concentration accounted for by the sample mean i two standard deviations as well as the term systematic error'1'* Hl which is equivalent to overall system accuracy. Relative standard deviation has also been used, and is defined as the equivalent of CV.051' Additionally, some authors report only raw data while others report means without standard deviations or sample sizes, and various other combinations. While all of these statistical determina tions have utility, it seems important for comparative pur poses to consistently use those determinations w hich give the most information in the simplest form. Certainly, bias and precision meet these criteria. Discussion of one other point seems necessary. NIOSH1101 has proposed as a guideline for their own internal purposes that sampling and analytical methods meet a minimum requirement of 25 percent accuracy*, that is, the absolute total error of the method should be less than 25 percent in at least 95 percent of the sample population (assuming a nor mal distribution). NIOSH derives the maximum precision value for an unbiased method given the accuracy criteria Stated. This value (12.8 percent) is the maximum precision value acceptable for an unbiased method. Although the 25 percent accuracy criterion has been criticized by some authors"6' it was adopted for NIOSH'sown internal use and is not meant as public policy. However. OSH A adopted the same criterion for the benzene standard, without a complete derivation or explanation. Consequently, this criterion has been criticized and alternatives have been proposed 07' A second important point is that bias is also considered in the 25 percent criterion according to a somewhat complex statistical relationship.00' but the overall system accuracy as defined earlier'1" is a fair approximation if the method has a true bias, i.e., its mean is statistically different from the "Known concentration." A final point is that as the number of samples at a level increases, the standard dev iation and CV should decrease. These considerations are important when evaluating passive monitor validation data, especially in those cases where manufacturers have stated that they have met the 25 percent accuracy criterion. For field comparisons of conventional and passive moni tors. different statistical tests are necessary. If passive moni tor values, for example, are plotted against charcoal tube American Industrial Hygiene Association JOURNAL (43) 8 8? results (Y vs. X) and more than one concentration is sampled, one would expect an increase in X to cause an increase in Y. If the increase is linear, and the sample values lie on the regression line, the correlation coefficient (r) would hav e a value of one. If a change in X brings about an equal change in Y. then the slope would also have a value of one. If the individual values for the two dev ices are indeed equiv a lent. the line should intercept the origin. Each of these rela tionships is expected within reason. The difference of the slop from one. the correlation coefficient from one, and the intercept from zero can and should be tested. In order to perform the regression analysis described above we must assume that X (active sampling data) is not subject to error. Of course, we Know and can calculate under laboratory conditions the error of active sampling systems There are at least three reasons why this error is olien overlooKed. First, it is assumed that consideration ol the error in X would only cause small diflerences in regression analysis results. Second, in addition to laboratory demon strated error, a range of errors introduced by varying envi ronmental conditions must be considered. 'While difficult to assess, these errors may have a profound effect on X. and indeed the error in the X measurement may be as great or greater than that for Y. Finally, if the error in X is to be considered the statistical tests are complex. Such tests have been discussed for biological problems:061 however, the the ories apparently have not been applied to sampling and analytical methods even though their appropriateness has been recognized.00' applications From a historical vantage, one of the earliest reports of a "passive" monitor for evaluation of airborne contaminants was patented by Gordon and Lowe in 1927.<20) Their gas detector for carbon monoxide inv olved an "easily frangible vessel containing a solution of salts including palladium chloride, and a covering for said vessel of a light colored absorbent material." The principle involved breaKing the vessel (a small ampule) and noting the subsequent color change of the solution as it reacted with the carbon monox ide on the light colored absorbent material. This type of semiquantiiaiive device was certainly a forerunner of those that are available today, though it was undoubtedly affected by air velocity as a stagnant air layer was not employed. An extension of Gordon and Lowe's concepts in the late I960's provided the basis for Plantz el al. to develop a personal dosimeter for measuring hydrazine, unsymmetrical dimethylhvdrazine and monomethylhydrazine.1211 The reac tion of these compounds with a "colorimetric substance" (bindone) produced a purple color, the intensity of which was dependent on both concentration and duration of expo sure. Color standards then were used to estimate the concen tration as a function of the time the badge was exposed to the contaminated air; consequently, the method was only senuquantitaiivc. In considering sources of error the authors noted that the purple color would also he produced by all volatile bases that were tested, including ammonia, aliphatic amines, aniline and cigarette smoKe. 3M 001500 609 Of interest in this review. however, are quantitative devices based on the principle of either gas or sapor diffu sion or permeation through a stagnant air layer. The first such des ice to be reported in the literature was described bv Palmesand Gunnison in 197_T1221 Their device employed the principle of gas diffusion to determine airborne concentra tions of sulfur dioxide and w ill receive further consideration subsequently. To gain the best overs iew of the various appli cations of these concepts, it is probably best to proceed bv considering first the inorganic and then organic gases and sapors. inorganic gases and vapors ammonia In 197S. Ma/ur rt ol. described the use of the Abcor GASBADGE to sample employee exposure to ammonia (this device currcnih is not marketedl.1*'" The investigators replaced the charcoal pad normally found in the G ASBADGE with an acid impregnated absorption pad Of three acids tested, phosphoric was most successful in pros iding the best approximation ol theoretical concentrations. They deter mined. howesci. that s olatile amines, specifically cyclohexy Iamine. could produce high readings, as high as 185 percent of the synthetic atmosphere. This led them to replace the glass fiberdraft shield on the front of the GASBADGE with a "charcoal impregnated glass fiber filter which had been pretreated with alcoholic KOH containing 0.1 percent sur factant." The charcoal sersed to adsorb amines as they dif fused into the dosimeter, while the KOH (aided by the wetting agent) eliminated irreversible ammonia adsorption b> the charcoal, w hich w ould ha\ e caused underestimation of the ambient concentration. Additional laboratory exper iments demonstrated that storage time of up to 47 days. pnortoanaKsis.did not appear to adversely affect the results. More recently. DuPont has developed a commercial!) available system for the measurement of several airborne contaminants including ammonia. In 1981. Kring et a!. described DuPont's PRO-1 EK'*system forammonia. nitro gen dioxide and sulfur dioxide sampling analysis using a col orimetric readout instrument.lJ'1' The ammonia badge relies on moleculat diffusion of ammonia and subsequent chemical reaction with a solution of0.3N boric acid and 0.03N sodium potassium tartaratefwV). After exposure, the reagent pack is removed from the badge holder and analysis is initiated by pressing reagent "blisters" which are adjacent to the absorb ing solution This action causes the release of a modified N'essier's reagent and the subsequent development of a colored solution. Forammonia. maximumcolor intensity is developed at 425 nanometers. The absorbance of the sample is then compared againsi a standard curve based on Beer's l.aw. After determination of the precision of the analytical method and verification of the linear range of the color chemistry. laboratory testing was conduct, d to establish the operational range as well os precision and accuracy of the overall method (see Table I) The minumumand maximum limits of the sampling range were found to be 50 and 500 ppm-hours. respectively, For an eight-hour time weighted average, these values correspond to oi.c-lourth and twoand one-halftimes the current ACGIH 1 hreshold l.imit Value of 25 parts per million.'21"'1 In considering sources of error, env ironmenial effects including temperature (10 to 40 C). relative humidity (10 to 80 percent), pressure (750 to 790 mm Hg). and face velocity (2.5 to 125 cm sec) were included. Of the env ironmenial factors evaluated, temperature and the concentration of the contaminant were identified as being responsible lor 98 percent of the data variation. For ammo nia. a temperature correction factor ofO ft percent per degree centigrade was suggested Also investigated was the storage stability of both unexposed and exposed badges. Results indicated that refrigerated storage is necessary toextend the shelf life of unexposed badges. Once the badge is exposed to ammonia and bclore the reagents arc mixed, the hadges can be stored for one (room temperature) to three (refrigerated) weeks without losing any absorbed contaminant. Once the reagents ate mixed and color formation is started, the badge should be read w ithin 90 minutes. Additional testing results conducted by DuPont arc shown in Table I >'h' carbon monoxide Shor and Anders, of the 3M Company. have described the 3M "direct-read diffusional monitor" for evaluation of exposures to carbon monoxide.<2,1 The principle involves the reaction of the carbon monoxide and an unreported reagent(s) to give a visible color change from pink to tan. Theoreticallv, "if anv pink color is observable at the end of the exposure period, then the exposure was less than the one time-weighted-average of 400 ppm-hours." They also state that noting the time to the endpoint allows for calculation of the average concentration of carbon monoxide during the exposure period. The authors present summary results of laboratorv evaluations using an infrared radiation dev ice to establish "know n" concentrations (see Table 1). chlorine Hard) et ol. have described a personal chlorine monitor (REAL. Inc.) which employs the principle of permeation of the gaseous contaminant through a silicone membrane and into 10 mL of a fluorescein-bromide solution.1281 Colorimet ric techniques then can be applied to determine the chlorine concentration. The authors report a detection limit of 0.013 ppm chlorine for an eight-hour exposure, with a "working range" of 0.1 to 2.0 ppm. Thev also suggest that for shorter time periods, concentrations of up to five ppm can be deter mined. Other observations included effects of temperature, humidity. absorbent concentration. pH and response time, with all laboratorv results presented graphically Moleculon Research Corporation has recently introduced a chlorine monitoring device which relies on plastic Film impregnated with liquid reagents.|2S) Exposure of the badge to chlorine gas gives a v isible. "blue-purple." color change. Optical transmission measurements, and comparison with a standard curve, can then provide quantitative exposures in ppm-hours The manufacturer's summary results indicating effects of temperature, humidity, wind v elocity and concen tration arc reported as presenting an error at the 95 percent confidence level, which is "less than 15 percent." 3H 00150]610 Air ho Hy[ Attoc J (43) Aufust 196? Chemical TABLE I Inorganic Gases and Vapors Laboratory Results Dosimeter* Bias" Preciaion' Range1' (ppm) Reference Notes Ammonia Nitrogen Dioxide Sulfur Dioxide Hydrogen Sulfide Mercury CO DP DP GB GB DP DP MDA GB DP DP GB 3M 3M 3M 0.5 05 -3.2 -3.2 -0 9 -4 9 -1 -08 0.5 17 0.3 7.4 69 9.3 21 7 76 87 4.1 13 8 58 75 15 3 9 2 47 20-50 20-48 6-62 4-11 4-11 4-11 6-9 4 6-5 3 4-11 4-11 16-2 2 0.03-0 3mg/m' 0 05-0 2mg/m 50-1830 24 26 23 1 38 24 36 1 38 24 1 32 33 27 rr N1 #:c; H1 <; *DP=DuPont Pro-Tek Colorimetric System Badges. 3M=3M Company Monitor, MDA-MOA Scientific, GB--Abcor GASBADGE "See text, equation (8) 1 See text, equation (7) "Some values are rounded to nearest whole number ''Bias consistently negative 'Results derived from Table III of McCammon er a/'"' "Results calculated from data provided in reference "This product is not currently marketed 'Bias could not be calculated from data given hydrogen sulfide In 1977, Tompkins and Goldsmith described the development of the GASBADGE personal sampler/1' Although later work with this device focused on the collection of organics on an actuated charcoal substrate, initial studies researched sampling of both organic and inorganic com pounds. (The GASBADGE for organic sapors is now mar keted b> National Mine Safety Company, and those for inorganic \apors are not currentlv marketed.) Applications in\ol\ ing inorganic gases relied on collective elements of an "appropriate substrate impregnated with a chemical medium specific for the contaminant of interest." Based on 60 obser vations. the authors' statistical summary is presented in Table I. Eighty percent of the measurements w'ere within 25 percent of the "true" value. Challenge concentrations were established in a "well-mixed" environmental test chamber and were measured with an "independent wetchemistrj sampling train." Hards and associates have described a permeation device (REAL. Inc.) which relies on the permeation of HjS through a dimethyl silicone membrane and subsequent reaction with a solution of 0.2N sodium hydroxide and EDTA.<30' The colored product (methylene blue) is measured spectrophotometrically and compared with a calibration curve to determine ppm-hours. A know ledge of exposure time then allows for the determination of average exposure over the measurement period. The authors note that a critical step in Amertcan Industrial Hygitn* Association JOURNAL (43)8 87 the dexelopment of such a device is the experimental deter mination of the permeation constant (see Equation 6), w hich inv olves calibration of each monitor by exposure to know n concentrations of the contaminant. The results of this lahorator> research demonstrated a detection limit of 0,01 ppm for an eight-hour exposure, w ith a working range ol 0.1 to 20 ppm and a linear response up to 200 ppm. The working range corresponds to one one-hundredth to two nme> the current eight-hour TLV of 10 ppm.1251 Evaluations ol env ironmental effects indicated that neither temperature, over the range of--3 to 39 C. nor humiditx. from 0 to 99 percent relative, caused any significant variations in response of the device. Further research demonstrated a good response to high concentrations in less than one minute, adequate sam ple stability up to 10 days if EDTA is used in the absorbing solution, and negative and positive interferences, respec tively, from chlorine gas and nitrogen dioxide. Precision and bias were not reported. Another approach for the determination of gaseous hxdrogen sulfide has been reported bv Gracdel and Franex.'31' Their research involved using a semiquantitativc method without a stagnant air layer and relv ing on the discoloration of lead-stabilized polyvinyl chloride (PVC). The technique involves the diffusion of gas in a polvmcr and. at high H2S levels, the detection rather than the measurement of toxic levels of H2S. Screening applications for low level exposures also are discussed. 3M 001502 sit mercury In 1977. McCammon and Woodfin of NIOSH reported the result1; of a laboratory evaluation of 3M's mercury vapor monitor/32'The monitor's operating principle in\olvesmolec ular diffusion and deposition of mercury vapor on a gold substrate The resulting change in electrical conductivity across the gold foil is related to the amount of mercury absorbed by the foil. Three other sampling methods, all of w hich in\ olved the active movement of air. also were inves tigated and include the LASL tandum sampling tube, the hopcalite tube, and the iodine impregnated charcoal tube. For the passive monitor, precision and accuracy, the effects of face velocity and temperature.and potential interferences were investigated. Concentrations of mercury vapor in an exposure chamber were monitored with an ultraviolet mer cury v apor meter, w hich in turn was calibrated by measure ments using the LASL method. To determine precision of the monitors, 12 devices were exposed to a test atmosphere. Results from th,rcc measurements of the test atmosphere using the LASL method gave an "expected" concentration of 0.056 milligrams of mercury per cubic meter of air (mg m3), with a standard deviation (SOI of 0.002 mg m3 and a coefficient of variation (CV) of 0.037. Precision and bias calculated for the data given in Table 111 of McCammon ei til.'3'' is summari7ed in Table 1. A least squares regression analv sis of the combined precision and accuracy results for the passive dosimeters versus the "known" concentrations gave a Y intercept of --0.004 mg m3 and a slope of 1.003. Tests for the effects of face velocities from 25 to 125 cm sec (50 to 250 1pm) did not appear to have any adverse effect on performance, w hile variation of temperature experimentally confirmed its effect on both the diffusion constant and the concentration of the contaminant. The potential effects of changes in relative humidity were not discussed by the authors. The other area of investigation in this study involved potential interferences of chlorine, sulfur dioxide, and hy drogen sulfide Concomitant and sequential exposure to mercury and chlorine, the latter at high levels (5.8 ppm), produced a negative bias, but a similar effect was observed with the llV meter and the LASL system. The authors suggested that the mercury and chlorine may have been reacting to form mercuric chloride which was not being measured by any of the systems. The interference effects of sulfur dioxide and hydrogen sulfide, although less than chlo rine. also were confirmed. In 1980. McCammon and his NIOSH and OSHA co workers conducted further tests of the four previously described mercury vapor samplingand analytical methods/33' The design of this laboratory experiment involved intercomparison of four methods, and the findings suggested that the variability of the iodine charcoal tube method is signifi cantly different from that of the other three methods. It was observed that the other three methods, including the 3M passive dosimeter, exhibited pood precision over the concen tration range of 0.05 to 0.2 mg m3 as shown in Table I. Recently SKC. Inc . introduced a gas monitoring badge (produced by GMD, Inc.) which uses the principle of molec ular diffusion (without a stagnant air layer) to collect mer cury vapor/341 The sampling media is referred to as "Hvdrar Sorbent."and "extensive"but unpublished field and labora tory testing are cited to show that "chlorine, moisture, etc., do not interfere" with measurements. HYDRAR is devel oped from a "manganese dioxide catalyst material similar to `Hopcalite.' " Quantitative determination is made by chemical desorption of the mercury and analysis with atomic absorption. nitrogen dioxide In 1976. Palmes etal. reported the results of their evaluation of a personal sampler for nitrogen dioxide (NO2)/351 This work was an extension of their earlier pioneering efforts in developing a personal sampler, employing the principle of gas diffusion, for sulfur dioxide.21 In their design, the sam pling device was a 1.3 cm (0.5 inches) acrylic tube. 7.1 cm (2.8 inches) long At the"c!osed"end of the diffusion path (tube) were placed three stainless steel grids coated with triethano lamine (TEA). TEA was selected because: I) it captures NO.efficiently. 21 it provides a stable sampling surface, and 3) it yields a chemical complex with NOj that is very stable over time. Subsequent analysts yielded a colored complex w hose absorption was measured at 540 nanometers. Results were then compared against a standard curve which obeyed Beer's Law. The experimental evaluation of the NO; sampler involved chamber measurements compared with "known" values determined by the volume of NO2 introduced to the chamber or the weight loss of NO2 from a permeation tube. Although neither indiv idual nor summary results were pre sented. graphical comparison of the data indicated a close agreement between the passive sampler results and theoreti cal concentrations. The effects of wind velocity and direction as well as stability over time also were considered. In deter mining wind effects, the uptake of water vapor, rather than NO*, was measured. The results indicated that there was an increase in average uptake with increased velocity and thai the 45 degree incident angle gave the highest uptake (135 percent at 258 cm sec). Across all angles of exposure (0 to 180 degrees) the average uptake increased from 2 to 14 percent as the wind velocity increased from 50 to 258 cm sec (100 to 516 fpm). Stability studies indicated that the badges could be used for months both after preparation and before exposure as well as after exposure and before analy sis. In the previously described studies with the GASBADGE. Tompkins and Goldsmith also monitored for nitrogen diox ide/11 Their summary results for 82 observations showed accuracies and precisions as summari7ed in Table 1. Eightyfive percent of the observations were within 25 percent of the "true" value A commercial model of the Palmes passive sampler has been marketed by MDA Scientific. Inc., and additional laboratory testing demonstrated a linear collection effi ciency for any given dose, i.e., concentration X time (see Table I)/31 The sampler exhibited a consistently negative bias as compared to concentration determinations using a continuous monitor and the NIOSH wet chemical method. As noted earlier, the DuPont PRO-TEK system includes a badge for nitrogen dioxide. Laboratory test results ol this device arc shown in Table l/3,1 3M 00150317 4m Inti Hff AsSOC J (43} Aufusr )9S; sulfur dioxide As noted previously, pioneering work in 1973 on the design of a sampling device which relics solely on diffusion of gaseous contaminants through a stagnant air layer is attrib uted to Palmes and Gunnison.,22> Their initial studies involved experimental work on different tube lengths. The collecting medium was a complex of mercuric chloride and the final analysis involved colorimetric determination. The studies demonstrated that, except for very short diffusion paths (tube lengths), the diffusion monitor satisfactorily duplicated the results obtained bv both wet chemical and conductrimetric measurements. Although this study did not go into the ramifications of environmental effects and inter ferences. it should be recognized as an important step in developing a new industrial hygiene technology. The last of the three inorganic gases looked at by Tompkins and Goldsmith in their studies of the GAS BADGE was sulfur dioxide."1 Summary data for 23 observations on this gas are included in Table I. One hundred percent of the observations were within 25 percent of the "true" values. The results from DuPont's tests on their sulfur dioxide badge also are shown in Table l.(3S) organic gases and vapors Most passive dosimeters designed to sample for organic gases and vapors use activated charcoal as the adsorbing medium. As we know from its extensive use in active sys tems, activated charcoal has an affinity for a wide range of organic compounds. Consequently, the discussion on the applications of passive dosimeters for the measurement of organic gases and vapors first will focus on devices using activated charcoal and then will turn to specific organics which rely on other collecting media. Chemical TABLE II Organic Gases and Vapors Laboratory Results Dosimeter* Bias" Precisionr Range1' (ppm) Reference Notes Carbon Tetrachloride Toluene Formaldehyde Benzene Ethylene Oxide Halothane Enflurane Acrylonitrile Hexane Vinyl Chloride Methyl Chlorolorm Tnchloroethyiene DPA DPA NMS DP DPB NMS NMS 3M 3M 3M NMS NMS R 3M DPA NMS 3M DPA NMS 04 03 -1.7 V5 33 -4 1 t .8 -14 3 -2.8 0 03 -1.2 -02 -59 -106 24 -3.9 -6 9 -05 44 525 1.7 63 4.7 1.7 17 3.2 74 48 87 2 37 47 45 2 76 77 1.9 3-18 57 228 12-47 0.2-4 2 3-24 08-54 13-13 5 300 0 5 20 0 5 20 0 7-19 10-37 1 5 14 160 840 160-840 15-65 20-200 20-200 15-67 10 fc 45 13 FJ 55 46 13 FJ 1 tc J 53 J 44 J 44 J 39 13 FJ 2 HJ 48 1J 48 LU 12 FJ 48 tJ 48 tu 12 FJ *3M = 3M Company Organic Vapor Monitor, DPA and DPB = DuPont PRO-TEK G-AA and G-BB Organic Vapor Badges. NMS = National Mine Safety GASBADGE. R = Real, InC MINIMONITOR. DP = DuPont PRO-TEK System Colorimetric Badges "See text, equation (8) rSee rext. equation (7) "Some values are rounded to nearest whole number ESmell sample sue FKnowns were calculated using charcoal tubes with critical orifices This could effect the bias measure ''Preliminary results "Permeation dosimeter 'Bias consistently negative ^Results calculated from data provided in reference Ammon induUMi Hygwnt Allocution JOURNAL (43) 8 S? 3H 00)504 13 ttvated charcoal devices s sii March. 1982. there were lour manufacturers of passive dimeters which rely on diffusion and subsequent adsorp>n on to actisated charcoal. National Mine Service (Tom my (GASBADGE). 7M Company (Organic Vapor Monirl. DuPont Company (PRO-TEK. G-AA and G-BR rganic Vapor Air Monitoring Badge), and the Mine Safety ppliance Company (Vaporgard Badge). In 1977, Tompkins and Goldsmith described the first mmercial passive dosimeter for monitoring organic jpors.'" The GAS8ADGE relied on moleculardiflusion of e vapor into the badge and subsequent adsorption onto mated charcoal The authors developed the theoretical nnciples of the badge's operation, and discussed sensitivity temperatuie and pressure, face velocity effects, and sponse time Preliminary results showing the badge's c^ponse 10 ben/ene. etlnl acetate, methyl ethyl ketone, and 'vrene also were presented and were described as "very icouragmg" (see Table II). I n the same y ear. Silverstetn reported results ol laboratory d t io Id testing ot the Ci AS BA DG E lor acrylonitrile Wl The suits ol the exposure ol 77 badges to known concenirams in the laboratorv are prevented in Table II. The results dicate the acceptability of the GASBADGE for measureents of aery lonitrile over the range ot 0.75 to 19 ppm. The ne of exposure in the laboratory was not given, however, eld measurements did cover periods of up to seven hours, though temperature and relative humidity ranges were ported, data analysis to determine the effects of these iriables was not ptesented, Silverstein also Evoked at .sorption efficiencies and determined that the best results `4 percent) were obtained with lour ml. ol two percent clone in carbon disulfide In 1978. Bamberger etal conducted a series oflaboratory sis to evaluate the GASBADGE Il-M Their approach involved e generation of known concentrations ol solvents and ibsequent ev aluation vv ith charcoal tubes (active sampling) nd the passive dosimeter. To evaluate the applicability ol ne dosimeter over a wide range ol compounds, the investiition included seven ditlerent organic compounds each ptesemauve ol a different functional group Included in 'his study were, benzene (aromatic), n-butano! (alcohol), n-buivl acetate (ester), isooctane (alkane), methyl ehlororm ( halogenated alkane), methy I isobuty I ketone (ketone), id trichloroethylene (halogenated alkene) The diffusion vetficient ( D) used was that supplied by the badge manufac.rer. except in the ease ot isooetane whieh was reported as iving an unknown coellicient Compulations involving ..us compound relied on the coefficient for n-oetane. A ' ariety of experiments was conducted to look at a wide range >f questions. Their findings corroborated dosimeter con cerns similar to I hose of acme systems using charcoal tubes. '* g., minimum and maximum loadings are important, poslimple comaminalion and loss can occur il the exposed hsorbent is not adequatelv sealed, percent recovery for nxiures is consistent with percent recoveries for single ompounds. and differences in charcoal lots can give diflernt results. Other tests confirmed (he need for some air movement across the badge lace and the lack ol elleci ol temperature changes over a small range I I I ( I 1 he results of the simultaneous sampling with the badges and the char coal tubes indicated that the badges had a consistent nega tive bias. The authors suggested that, because the results were so reproducible, corrections lor adsorption dcsoi ption efficiencies less than 100 percent can be accomplished lust as is done for charcoal tube data In 1979, Hirayamaand Ikeda evaluated the application ol the G/VSBADGE lor monitoring exposures lo mixed sol vents.Their research involved ditlerent pieparations ot activated carbon "felt" in place ol the supplied collection medium and exposure to mixtures of n-he\ane. ethy I acetate and toluene. Summary (graphical) data indicated that the amounts of contaminant absorbed by the dosimeter were proportional to both the vapor concentrations and time ol exposure, Hallidav and Anderson reported on the use ol the GASBADGE in monitoring loi lialothane 11 Six observa tions indicated a rangeol measurements Irom minus nine to plus ten percent ot the test atmospheres I'nlortunately. the authors did not report their procedure for determining the concentration ol halothane in the test atmosphetes In 1981. Evans and Horstman reported evaluations ol desorption efficiencies of charcoal tubes and the G AS BA DOE for stv rene 'J''' For liquid dosing they lound the dosimeter to be similar to the tube, w hile for vapor dosing the badge was superior The authors suggested that the difference' in results may have been related to the use of coconut shell carbon in the tubes and petroleum derived carbon in the badge. They did not explain w by this difference would affect one method of dosing and noi the other. In 1980. Anders and Mullins of the 7M Company pre sented results comparing the 7 M passive monitor with char coal lubes in sampling for mixtures of organic compounds 1' " The laboratory tests included a binary mixture of toluene and methyl ethyl ketone: a tertiary mixture ol benzene, toluene and xylene, and complex mixtures ot unleaded and leaded gasoline containing various alcohols. Although the investigators cited "excellent" precision and accuracy for the ditfusional monitor, sample sizes were small, and the com plicated study design and lack of raw data preclude the determination of precision and bias statistics. Mazur and his co-workets,m conducted side-by-side laboratory and field tests with charcoal tubes and 7M organic vapor monitors to measure concentrations of halo thane (2-bromo-2-chloro-l. I.I-trifluoroeihane) and enflurane (2-chloro-1.1.2-trifluoroethvl difluoromethyl ether). The results of the laboratory studies are presented in Table 11 and support the authors' conclusions that the dosimeters are a reliable method lor the collection of enlTurane and halothane In 1980. I autenberger ei at. described DuPont's passive monitor for organic vapors.'1" Each chatcoul strip in the PRO-TEK G-AA Organic Vapor Badge contains approxi mately 700 mg of coconut-based activated charcoal impreg nated in an inert poly mer. A dual sampling rate of apprnxi- 3H 001505 km Ind Assoc 1(43) Autfus? 198? mutely 50 or 100 ml mm in determined by the removal ol one or both ol the dosimeter's protective covers. One aspect ol their research mv olved experimental determination ol the dillusion coefficient of several gases and vapors They reported that values calculated by I tigg'*' were within 10 percent of their experimentally determined diffusion eoellicient values. Preliminary experimental results were used to discuss lace velocity el feels, ranee and sensitivity, maximum and minimum sampling limes, vapor retention, storage sta bility. desorption efficiency, and overall badge efficiency. 1 he overall accuracy determinations were limited to four observations at each of two concentrations of carbon tetrachloride (see Table 111 However, the presentation of raw data, as well as an explanation of the statistical tests applied, is most useful. This same detail of information is also found in DuPont's validation reports for toluene and ben/ene (see Table II).'1' In the ben/ene report. DuPont also describes its PRO-TEK G-BB badge This badge has a backup section ol charcoal, which serves the same putposc as the second section in a charcoal tube. /.t\. to aid in determining it the sampler has heen overloaded. I he 3M Company also markets an Organic Vapor Monitor with a backup section,'1 1 In studies of the measurement ol waste anesthetic gases with passive dosimeters. Jonas m at. evaluated the CiASBADGE, 3M Organic Vapor Monitor and DuPont Pro-Tek in measuring enlluranc.'*1 Unfortunately, the badges were not identified in the presentation of the resultsalthough interpretation of the reported sampler geometry would indi cate that A was the DuPont badge. BwasiheJM badge.and C was the CiASBADGE. The results ol their laboratory studies indicated that badge B had the lowest coefficients of variation (CV was not calculated as described in this text) as compared to concentrations determined by infrared analy sis. Badge A had a low CV (9 percent) at 5 ppm and a much higher value (CV=34 percent) at 20 ppm. The C badge had consistently high CV's ranging from 23 to 30 percent. It should also be noted that the charcoal tube CV's ranged from II to 27 percent, that desorption efficiencies for the badges ranged from 0 81 to 1.17. and that IR analyses of tank concentrations were constantly lower than expected. If badge B was the 3 M dev ice. the results of Jonas ei al. support those reported by Ma/urer at.'"' Further testing of badges A and C seems necessary, however, to confirm their seemingly low precisions. Ma/ur and his coworkers conducted additional tests comparing the 3M and DuPont badges against charcoal tubes ,l" Methyl chloroform and trichloroethylene, two sol vents widely used in vapor degreasing operations, were sampled. In the laboratory phase of the study, the badges and charcoal tubes were exposed to chamber concent rations over the range of 160 to 840 ppm of methy l chloroform and from 20 to 200 ppm of trichloroethylene. Exposure times varied from two to six hours for methyl chloroform and from four to six hours for trichloroethylene. The laboratory work indicated that the percent recoveries of the various doses (concentration X time) were in good agreement except for one exposure of the 3M badge which involved a five hour Wctm industrial Hygiene Allocution JOURNAL (43) 8.82 exposure at 700 ppm. T he authors noted that this exposure ol 3500 ppm-hours exceeded the upper exposure limit pro vided by the manufacturer. The overall mean recovery value lor each tv pc of sampler was used to correct till subsequent lield data. In addition to the recovery measurements, the laboratory phase of this study also involved determination ol storage stability. The authors found no significant losses of methyl chloroform or trichloroethylene I rom either badge following storage of exposed badges for up to three weeks. In 1978. West and Reis/ner reported on the field tests of the MINl MONITORTM (REAL. Inc.) permeation personal monitor for vinyl chloride.This monitor was a modified version of one previously described by Nelms et al."*' 1 he collecting medium was activated charcoal, but rather than reiving on molecular diffusion, the badge design involved a polymeric membrane and the permeation of vinyl chloride through the membrane and adsorption onto the charcoal Initial laboratory calibration was used to determine the permeation constant of the dev ice. Laboratory results indi cated good accuracies as summarized in Table II. During the same period that Tompkins and Goldsmith'1 were describing the GASBADGE. Bailey and HollingdaleSmith of Great Britain were presenting their ideas lor a personal passive sampler for organic gases and vapors. Their design involved the use of either one of two types of membrane and subsequent adsorption onto activated char coal. They found two membranes to be satisfactory: one of thin silicone rubber which acted as a permeation harrier, and the second a porous polypropylene film which allowed lor molecular diffusion of the gas and vapor. They conducted laboratory tests using carbon tetrachloride, styrene and dichlorodifluormethane. Their test results do mix some ter minology. e.g.. permeation rates for both the permeation device and the diffusional device, but did provide an early demonstration of the feasibility of such a dev ice for monitor ing certain organics. The device, the Porton Dillusion Sampler, seems to see its greatest use in Great Britain. acrylonitrile One of the newest applications of passive dosimetry involves the use of a porous polymer f Porapak N) as the collecting surface with subsequent thermal desorption and gas chro matographic analysis. Benson and Boyce have described such a device and its utility in sampling lor acrylonitrile Laboratory testing for acrylonitrile involved comparison of the dosimeter values with concentrations measured on a gas chromatograph. Initial experimentation indicated that the dosimeter can be used for acrylonitrile concentrations in the range of 4 ppm. but at concentrations of 2 ppm a 40 percent error is reported. aniline In addition to activated charcoal, another widely used adsorbent medium is silica gel. To study the utility of this material. Campbell and Kon/en constructed passive dosim eters from glass culture tubes (1.05 cm inside diameter) with 40 60 mesh silica gel as the collecting surface.'5,1' Laboratory testing involved exposure of the dosimeter to aniline, with exposure concentrations determined by gas chromato graphic analysis of ethanol gas scrubbers. Three different 3H 001506 SIS -i7e (length) dosimeters were e\aluaicd. with the best results obtained w ith the intermediate length tube(L = 3.0cm: A L = 0,3 cm). The authors present raw data and clearly described their statistical techniques. ethylene oxide Mullins and Anders have recently described the 3M diffusional monitor for sampling ethylene oxide in air.<Ml In this badge the collecting surface is described as a "chemically impregnated charcoal surface, (where) a reaction occurs producing a stable compound with a \apor pressure sub stantially lower than the parent compound." The authors present statistically summarised data describing the linearity and capacity of the monitor, the recovery of absorbed ethyl ene oxide. cn\ironmentul effects, sample stability, and the effects of potential interferences. Precision and bias are presented in Tabic II. formaldehyde Rodriguez ei at ha\c described another 3M diffusional monitor for sampling formaldehyde.In this diffusional monitor, the collecting surface is an "impregnated sorbent" which can then be desorbed in situ with water and the concentration of formaldehydedetermined colorimetricallv. Laboratory evaluation first involved determination of recov ery coefficients, which at eight ppm-hours (I9.S micro grams) were found to be 1.00 0.04 over six tests. The next step involved determination of the dosimeter's "sampling rate" (DA l) by exposing the dosimeters to "known" con centrations of formaldehyde as generated by a permeation tube The effect of relative humidity on the sampling rate also was investigated, and evaluation of the data did not indicate any statistically significant differences between the rates at 50 and 85 percent relative humidity. The study protocol then inv olved simultaneous exposures of impingers (modified chromotropic acid method) and dosimeters. The authors concluded that "the measured values by both methods lie within 25 percent of the expected response" and that "less variation is observed in the monitors than in the impingers." However, neither precision nor bias were reported. The authors also investigated effects of storage and determined that at elevated temperatures (38 C) losses up to 11 percent occurred after one week, however no signif icant loss was seen for samples stored at 23 C. The authors briefly discussed the potential for a negative interference from phenol and described the use of modified calibration curves to address this problem. DuPont's PRO-TEK series of colorimetric Air Monitor ing Badges, includes a badge for formaldehyde. The collec tion principle involves a chromoiropic acid-sulfuric acid reaction. Laboratory cvaluation(42samples)ofthcdcviceal seven exposure levels revealed results as shown in Table II Additional studies also were conducted on tempera ture and storage effects The raw data and statistical analysis procedures arc presented Kriesel156' has described a new passive dosimeter for form aldehyde which is a modified version of the Palmes tube. At the present time experimental data concerning this dev ice are not available 16 phosgene Matberne ei at. have recently described the GMD. Inc "passive dosimcter"w hich prov ides a semiquantitativc mea surement of phosgene exposure.<s'' The badge involves direct contact between the contaminated air and a chemi cally impregnated tape and therefore does not rely on a stagnant air layer. The treated paper stain intensity is reported to he logarithmically proportional to the phosgene doseovera range of2to 100 ppm-minutes. For quantitative measurements the badges can be read colorimetricallv. other methods Hill and Fraser have described the use of commercial detec tor tubes modified to act as passive dosimeters l'v` In then research, common length-of-stain detector tubes were modi fied by cutting off the conical end of the tube and renvov ing some of the indicator column material. This leaves an oritice with a cross-sectional area equal to that of the inside of the tube and a path length determined by the distance from the end of the tube, to the beginning of the indicator material One would expect, however, that as the sorbent matcnal becomes exposed, i.e.. the length of stain increases, the diffusion path length will also increase, thereby changing the sampling rate. Their evaluation of these devices involved separate laboratory exposures to toluene, ethanol and I'Opropanol. The results of their work, although presented only in graphical summary, demonstrate the potential for the use of modified commercial detector tubes as passive dosimeters field validation Relatively few studies have been published in which passive dosimeters have been compared side by side with chaicoal tubes or other conventional sampling methods under actual field conditions. For inorganic compounds only two stud ies. involving nitrogen dioxide159' and chlorine. have been identified. For organic compounds, eight stud ies15 9 39 4,145,5160611 inN0)xed field comparisons, with the number of compounds per study ranging from one to 22, In three of these studies, statistical analyses of data were not presented and cannot be performed because of small sample size or insufficient presentation of data. Jones et at.'h91 conducted a field evaluation for NO_> in a salt mine, which contained diesel equipment as the NO.source. At each of 16 different fixed area locations, two Palmes dosimeters and two TEA tubes with pumps were used to sample the atmosphere. The active sampling (pump) method gave a coefficient of variation (CV) of 8 7 percent while for passive tubes the CV was 5.8 percent. Regression analysis (where the active system was the X variable) of their data gives a correlation coefficient of 0.69. a slope of 0.59. and an intercept of 2,05 ppm for data over the range of 3.7 to 5.5 ppm as sampled by the active method. This indicates that the dosimeter gave consistently higher readings which is reflected in the means for the two methods 4.51 ppm lot passive and 4.14 ppm for active sampling. The authors did not report wind velocities, but low velocities, as would be expected with area samples, should have caused passive 3H 001507 4m tna Hyf 4ssoc \alue.s lo be low as compared 10 active values; this was not the case. On the other hand, high face velocities could have led to the observed positive (passive versus active) bias. Hardy el al.m reported the raw data results from a Held evaluation of a permeation chlorine monitor (REAL. Inc.). Thirteen comparisons were made in which the results from a batters operated pump and an impinger sampler were com pared with the measurements from either two or three per meation samplers. To further evaluate their results, the investigators performed a regression analysis using their permeation sample means for each comparison as the dependent variable. The results are quite good with a corre lation coefficient of 0.95. a regression slope of 0.85. and an intercept of 0.15 over a range of 0.03 to I. I ppm as detected by the inipmgcr It should be noted that with five impinger samples o( less than 0.1 ppm. the corresponding permeation dev ices detected considerably higher concent rat ions (0.16 to 0 4 ppm) Silvcrvtcin,,li' reported field results for acrylonitrile moni toring UMng 18 paired samples of GASBADGE passive monitors and active systems (charcoal tubes and pumps) over a range of 0,8 to 3.8 ppm as determined by the active method The differences in results using the active system as a reference ranged from --0.7 to 1.5 ppm. The difference in means, 2 18 for the passive versus 2.73 for the active system, was 25 percent. Further data were not presented. W est and Rcisznet reported five sets of Field results for viny I chloride sampled with permeation dosimeters (RE A L. Inc ) and charcoal lubes.''' Further interpretation of their results is presented in Tabic III. In each case data for the active system are the X values. Four of the correlation coefficient values are very near one. reflecting good correla tion. however, the slopes show quite a large degree of varia bility (0.69 to 1.31). indicating that badge values may fall either well below or above charcoal lube values. In those cases w here the slopes were less than 1.0. very high humidi ties (67 to 91 percent) were reported by the authors. This factor may have interfered with permeation, although the authors reported that humidity had no effect in laboratory validations; hence the variation in slope remains unex plained. The authors noted that the overall field results showed that the badges had a slight positive bias Hickey and Bishop exposed 78 pairs of side-by-side char coal tubes and 3M Organic Vapor Monitors to complex mixtures of organic chemicals in tire manufacturing opera tions Generally the sampling period ranged from three to TABLE III Regression Analysis of Vinyl Chloride Field Data13' N Range (ppm) r Slope Y-Intarcept 7 002-1 0 99 1 19 8 0.08-1 8 0 99 069 12 0 02-6.9 1.0 1 31 39 0.05-1 8 0.82 0.81 24 1 48 16 7 0 96 1 08 003 0 05 0.01 0.11 0 43 Ametican Industrial Hygtfnf Association JOURNAL (45) 8282 five hours, and most observations consisted of one monitoi and the time weighted average concentration front two sequentially exposed charcoal lubes Sixty-four of the sets were personal samples, while the remaining 14 were aiea samples. The samples were collected in two separate plants (30 sample pairs in one plant and 48 in the other) Ot the 22 organics potentially available for analysis. 10 were detected over a sufficiently w ide range of concentrations to allow lor appropriate statistical analysis by linear regression The results are interesting in that in the first plant. 9 of the 10 organics measured by the dosimeters showed higher vapor concentrations as compared to the charcoal tubes, while in the second plant only three substances had a regression slope greater than one. The combined data for both plants did not indicate that the passive system was consistently biased when compared to the active system. The authors did point out that generally the 3-intercepts (Y=passive dosimeter data) were slightly negative, a finding w hich may indicate a lack of sensitivity on the part of the dosimeters at low concentrations. For the remaining 12 compounds, paired t-tests revealed no significant difference between the char coal tube and passive monitor means at the 95 percent confidence level. The use of t-tests to analyze such data has been questioned since the means of the two methods mav be very similar but the components of paired values can be considerably different.<l9) This condition can only be revealed through regression analyses. In 1980. Mazur el reported limited field data for halothane and enfiurane measurements using both 3M Organic Vapor Monitors (OVM) and an active system (charcoal tubes and pumps). For halothane three paired samples were reported. The mean concentration for the active system was 2.01 ppm while 1.9 ppm was reported lor the OVM. a difference (relative to the active sy stem) of five percent. Only one data pair was reported for enfiurane: 0.49 ppm for the OVM and 0.52 ppm for the active system Obviously, more data are needed to draw conclusions regarding a comparison of the two methods for these agents A second study by Mazur el al,m' reported field compar isons of passive dosimeters and active systems (pumps and charcoal tubes) in sampling for trichloroethy lene (TCE (and methylchloroform (MC). Both DuPont PRO-TEK and 3M Organic Vapor Monitors were used for the passive systems Personal samples included exposure of one each of all three monitors. Area sample results involved threeaverage values: one was the average of three charcoal tubes, and the other tw o. the average of two of each type of dosimeter. For M C. 11 personal and 7 area data points collected over time peri ods of I to 5 hours at 15 to 21 C and 35 to 40 percent relative humidity were reported. For TCE. 22 personal and 7 area data points collected over periods of about I to 6 hours at 18 to 24 C and 30 percent relative humidity were reported. A regression analysis in W'hich the charcoal tubes were the independent variable was reported by the authors. In each of the following data sets the presented values involve TCE personal and stationary sampling followed by MC personal and stationary sampling. For the DuPont badge, regression 3M 001508 slopes of 1.0, 0.99, 0.99. and 0.98, and correlation coeffi cients of 0.98,0.98.0.94, and 0.94 were obtained. For the 3M badge, regression slopes of 1.08, 1.06, 1.07. and 0.90, and correlation coefficients of 0.98, 0.98. 0.98. and 0.90 were determined. These values appear to be quite good: however, the authors did not report if they tested the statistical signifi cance of these values. They also did not report average of face velocities associated with stationary samples. Evans ei ol.<m of Great Britain reported field validation data for the Porton diffusion dev ice while measuring methyl ethyl ketone. In this case the conventional sampler was a pump and a cassette fitted with a charcoal cloth similar to that used in the Porton device. A regression analysis per formed with their data showed good correlation (0.9) and good slope (0.9); however, the intercept value (4.69) indi cated that, at low concentrations, the "home-made" dev ice gave lower values than those determined with the conven tional monitor. Concentrations reported for the conven tional device ranged from II to 189 ppm. Benson and Boyce,Ml field lested the Monsanto Poropak v dev icc in Great Britain. Conventional samplers consisted of pumps and Poropak N polymer tubes. Sixty-five pairs of samples were obtained, and the range of acrylonitrile mea sured by the tubes was 0,13 to 21.65 ppm. Regression analyis of their data indicates only fair correlation (0.63). a low .lope (0.46). and a negative intercept (--2.06). These values vppear to result from the apparent inability of the passive lev ice to accurately detect concentrations less than 0.5 ppm. A! so, comparisons between values over the lower half of concentrations sampled showed considerable scatter. The final field study to be discussed suggests perhaps the most serious discrepancies resulting from use of charcoal passive dosimeters,<6" This study was performed by NIOSH versonnel in conjunction with industry-wide studies of the lry-cleaning, screen printing, and boat manufacturing indusries, and also included one viscose rayon and one celloihane plant. Carbon disulfide, pcrchloroethylene. toluene, metbylisobutyl ketone (MIBK). styrene, and acetone were ampled using the 3M OVM. the GASBADGE, and active ystemx with charcoal tubes. The presentation of the study design is not clear, but it appears that area samples involved all three devices while personal samples involved charcoal tubes and only one of either passive dev icc. In that this study nvolves six compounds in 64 plants, the volume of data is juite large. In addition to regression analysis, paired t-tests rnd Wilcov signed rank tests were performed by the authors o determine equivalence of data sets. As noted earlier he use of t-tests for determination of equivalence has been questioned.'19' Table IV shows the primary results of this study. As can be seen, the range of correlation coefficients <r) for most com pounds was quite large. Although 12 plants were sur veyed for toluene and MIBK. ihe data ere grouped ngether. and therefore ranges of the correlation coefficients ould not be determined. For carbon disulfide, one plant as surveyed w ith the OVM and GASBADGE. and one was urveyed with the GASBADGE only. Foi the ranges of r .ported in Table IV. the upper values are quite acceptable. with the exception of carbon disulfide using the G ASBA DGE. However, the correlation coefficient for carbon disulfide using the OVM was 0.95. The correlation data can be summed up as being extremely variable. Table IV also reveals that concentration had an effect on the correlation coefficient for three of the compounds, though this was true for both monitors only w hen measuring acetone concentra tions. Regression slopes were as variable as the correlation coefficients. The authors tested the slopes to sec if they were significantly different from 7cro.and for acetone and carbon disulfide a difference could not be demonstrated for several -of their data sets. This indicated that there was no relation ship between the results obtained w ith the active sy stem and those obtained with the passive dosimeter. For other com pounds. ii would have been useful to lest the difference ol the slope from one. which if not significantly different would indicate agreement of the two methods. In tests of equivalence of data sets, the authors noted that for all plant data combined, only toluene showed equality, and this for the charcoal tubc-GASBADGE (CT-GB) com parison. However, when results from individual plants arcused, the comparison outcomes arc quite variable. For pcrchloroethylene, equality was reported for one of three CT-BG comparisons and for one of two CT-3M sets. For styrene, two of six CT-GB and no CT-3M comparisons showed equality. Foracetone. three of five CT-3M compari sons and one of six CT-GB data sets showed equality . In addition. GB-OYM comparisons showed equality in 6 of 17 comparisons. It is obv ious that repeatability was not demon strated in this study. Whether the problem involves the dosimeters, investigative or laboratory techniques, and or environmental conditions cannot be determined. In Ihe only other field study of more than one plant, Hickey and Bishop19' also reported some problems w uh the consistency of observations. These limited results clearly demonstrate the need for additional field studies of passive dosimeters as compared with standard monitoring techniques. discussion Passivedosimeiry (monitoring) isa rapidly developing tech nology as witnessed by the proliferation of devices and applications since Palmes and Gunnison introduced their concepts just under ten years ago.12'1 The latest entry into the field comes from the MSA Company and inv olves an adap tation of their length-of-stain direct reading tubes for inor ganic gases192' w hich incorporates the application of molecu lar diffusion and a chemically impregnated paper as the sampling medium. Although research results arc not availa ble, as a first approximation one might assume that these devices have precisions and biases similar to those of con ventional detector tubes For any new technology to be accepted and used by piacticing professionals, the development of a body of knowl edge demonstrating efficacy is necessary. With env ironmental monitoring techniques, the determination of the efficacy usually starts in the laboratory and culminates in the field. In the case of passive monitors, a body of knowledge based on laboratory testing is rapidly being developed Of the vari- 3M 001509 Am Inti Hvf: Assoc J(A3> AupuM 19T TABLE IV Major Results of a Field Study for Organic Vapors'*1' Concentration Substance Comparison Overall r Range of r Dependency Perchloroethylene Styrene Acetone Toluene MIBK cs CT-GB CT-3M CT-GB CT-3M CT-GB CT 3M CT GB CT-3M CT GB CT 3M CT-GB CT-3M 0 62 0 86 0 82 0 76 0 38 045 0 80 091 0 88 0 79 0 30 0 95 0 62-0 99 0 84-0 94 065-097 0 48-0 86 0 36-0 86 0.25-0.83 NA NA NA NA 0.03-0 38 NA Yes Yes Yes Yes ables that have been studied, threeappearto unique!) aflect a diflusion monitors accuracy in nieasurinp airborne concen trations of gases or \apors. T he most important factor appears to be determination of the contaminants' diflusion coefficient (or the sampling rale when the dosimeter's geometry is also considered), the wind \clocity at the dosimeter lace, and the relative humidity of the sampled air. As discussed earliei. there are also a variety of potential sources of error, such as interlcring contaminants, sorbent capacity and problems associated withanahticaldetcrminations, which are common to both passive and active mea surement techniques. Laboratory determination of sampling rates! DA l.) fora specific monitor and a specific contaminant are important and are being prov ided by several dosimeter manufacturers for an ever increasing number of compounds. Once an appropriate sampling rate has been determined, corrections lor field use. specifically for temperature variations, can be made The main problem would involvcsituations where the env iron mental temperature fluctuated widely (more than 25 C) and went unnoticed, a very unlike!) condition. The research on effects of lace v clocities demonstrate that few problems should be encountered where dosimeters are worn by workers as personal monitoring devices.*1 Their use as area monitors should be carefully evaluated to ensure that stagnant atmospheres (velocities less than 7.5 cm sec)arc not involved. High wind vclocities(at least what would normally be encounteied in the workplace) or wind direction do not appear to have adverse effects on dosime ters with wind screens. Of greatest concern as a result of rev ievving the literature on laboratory testing of passive dosimeters is not the results but rather the thoroughness of their presentation. As dem onstrated in Tables I and II. where statistical analyses arc presented bv researchers, or where sufficient data arc pre sented toallow the reader to determine biasand precision, the rcsultsarc very encouraging. Unfortunately the presentation of experimental design, as well as sufficient data and or statistical analyses, are often lacking. This is true lor some Am*rcn industml H>p*nt Allocution JOURNAL (43 8 8? indiv idual researchers as well as for several manufacturers ol the dev ices, especially those for inorganic compounds If one recommendation regarding laboratory testing is made, it would be that those researchers involved in the evaluation ol passive dosimeters in the laboratory take the time to report the conditions of their experiments, especially equipment used and procedures for determining "known" concentra tions. and as much detail about their results as possible. If summarized data arc presented, the author should present the known concentration at each level, where levels are determined by concentration and time, the number of obser vations made with passive dosimeters, and the average value and standard deviation of the results. Statistical analyses, again at each level tested, should involve determination ol the coefficient ol variation (precision) and the bias as described in equations (7) and (K). respectively. Once the evaluations are made at the various test levels, the determi nation of a pooled precision and bias is appropriate. In addition to these measurements, researchers may also choose to present an overall system accuracy 1 o develop a better understanding ol appropriate statistical techniques and their application to passive dosimetry, a review of l.auicnhcrgcr el al. is recommended.111' For most active monitoring systems used in industrial hygiene the random sampling error is usually associated with the pump and is traditionally set at 5 percent,'1"' In many cases, especially lor the measurement of organic vapors, the analytical procedures and consequently their associated errors arc equivalent lor both passive and active systems. Nevertheless, both systems have random error: consequently, one should not expect perfect agreement of the results of comparisons obtained under field test condi tions. Another factor complicating the evaluation ol field results is the greatly increased possibility for the introduc tion ol operator, or systematic, errors. Since active systems require mechanical pumps, the potential for operator error would seem to be greater than for passive systems. Overall, it is apparent that existing field observations comparing passive dosimeters with standard monitoring methods are highly varied. While some studies demonstrate good correlation and slope.'*1others show only good correlation.1* or arc extremely varied for both categories."'1 Collectively, these references neither support nor refute the use of passive dosimeters. Certainly environmental lactors affect active sy stems as well as passive systems. In theory . a case can be made that environmental factors (wind and humidity (affect passive systems to the greatest extent, while temperature and pressure variations most greatly allect active systems. On the other hand one can also state that poor experimental quality control may affect such factors as contamination, time measurement error, and analytical error. Of course, chemical interferences may aflect both systems. As with laboratory experimentation, recommendations regarding the field testing of passive dosimeters involve a plea for better reporting ol both field conditions and results of analysis. First, for both personal and area monitoring, the estimation and or measurement of face velocity is impoi- 3M 001510 619 lant Of equal importance is the reporting of airborne con taminants other than the one(s) of interest and env ironmental variables including temperature, pressure, and relative humidity along with information as to their variation over ;he period of observation. Again, if raw data cannot be presented, the reported results for each level tested (X value as determined by the standard method) should include the number of observations made with passive dosimeters, and heir associated mean and coefficient of variation. Statistical evaluations also should include a regression analysis of the data as outlined earlier Undoubtedly, additional research is needed on the effect of not considering the error associated A ith the supposedly independent (X) variable. In summary, passive dosimeters show great promise as an mportant tool. The results presented in Tables I and II ndicate that the precisions of the dosimeters are essentially equiv alent to conventional techniques and in many cases the additional five percent error associated with mechanical lumps makes passive dosimeter systems even more attracivc. This, coupled with their ease of use, lack of required oamtenancc. acceptance by w orkers due to light weight, and mnecessary calibration make passive dosimeters extremely idvantageous Certainly they will not replace conventional nethods. as these have their place, especially for area sam>ling. The continued and growing use of passive dosimeters, owever. should generate additional data documenting their ^liability and eliminating doubts about their usefulness. cknowledgement he assistance of Dr H. Kenneth Dillon. Head. Industrial fygicne Chemistry Section of Southern Research Institute. n critically review ing t his paper is gratefully acknowledged. eferences 1 Tompkins. F.C and R.L. Goldsmith: A New Personal Dosimeter for Monitoring of Industrial Pollutants. Am Ind Hyg Assoc J 38 371-377(1977), 2 West. P.W. andK.D. Retainer: Field Tests of a PermeationType Personal Monitor for Vinyl Chloride Am, Ind- Hyg, Assoc J 39 645-650(1978) 3 Lugg, G.A.: Diffusion Coefficients of Some Organic and Other Vapors m Air Ana/ Chem 40 1072-1077(1968) 4. Montalvo. J.G.: Total Elemental Content Passive Personal Monitors. Am Ind Hyg Assoc 3.40 1046-1054(1979) 5 3M Company: Organic Vapor Monitor Sampling Rate Vali dation Protocol St Paul, MN 5 Jonas, L.C.. C.E. Billings, and C. Litis Laboratory Perfor mance of Passive Personal Samplers for Waste Anesthetic Gas (Enflurane) Concentrations. Am. Ind Hyg Assoc J. 42 104-111 (1981) 7 Woebkenberg, M.L.: Current NIOSH Research on Passive Monitors. In Proceedings of the Symposium on the Develop ment and Usage of Personal Monitors for Exposure and Health Effect Studies, pp 27-33, Evironmental Protection Agency, EPA - $00/9 79-032 (1979) 8 Environmental Protection Agency: Laboratory Evaluation of Commercially Available Passive Organic Personal Moni tors Contract Number 68-02-2686 ) Hickey. J.L.S. and C.C. Bishop: Field Comparison of Char coal Tubes and Passive Vapor Monitors with Mixed Organic Vapors Am, Ind Hyg Assoc J 42 264 267 (19811 0 10. U.S. Department of Health. Education, and Welfare: Doc umentation of NIOSH Validation Tests. NIOSH 77-185. Cincinnati (April, 1977) 11. Lautenberger. W.J.. E.V. Kring, J.A. Morello: A New Per sonal Badge Monitor for Organic Vapors. Am. Ind. Hyg Assoc J 41 737-747 (1980). 12. Bamberger, R.L..G.G. Esposito, B.W. Jacobs.G.E. Podotak and J.F. Mazur; A New Personal Sampler for Organic Vapors, Am. Ind Hyg. Assoc J 39 701 -708 (1978) 13. National Mine Safety Company: GASBADGE Product Bulletin Chlorinated Solvents Performance Date. Oakdale. PA (1979) 14. National Mine Safety Company: GASBADGE Product Bulletin Aliphatic and Aromatic Performance Data. Oakdale. PA (1979) 15 Anonymous: Guide for Use of Terms in Reporting Data in Analytical Chemistry Anal. Chem. 52.221 (1980). 16 Shotwell. H.P., J.C. Caporossi. R.W. McCollom and J.F Mellor: A Validation Procedure for Air Sampling Analysis Systems Am Ind Hyg. Assoc. J. 40:737-742 (1979). 17. D'Agostino. R.B. and J.L. Gillespie: Comments on the OSHA Accuracy of Measurement Requirement for Monitor ing Employee Exposure to Benzene Am Ind. Hyg Assoc J 39-510 513(1978). 18. Carlson, F.D., E. Sobal and G.S. Watson: Linear Relation ships Between Variables Affected by Errors. Biometrics 22 252-267(1966) 19. Tuggle, R.M.: Incorrect Use of f-Tests Am. Ind. Hyg Assoc. J 42.325-326(1981). 20. Gordon. C.S. and J.T. Lowe: Carbon Monoxide Detector. U.S. Patent 1,644,014(1927). 21. Plant*, C.A.. P.W. McConnaughay and C.C. Jenca: Colori metric Personal Dosimeter for Hydrazine Fuel Handlers. Am. Ind Hyg Assoc. J 29 162-164 (1968). 22. Palmes. E.D. and A.F. Gunnison: Personal Monitoring Devices for Gaseous Contaminants Am Ind Hyg. Assoc J. 34 78-81 0973) 23. Mazur, J.F., R.L. Bamberger and G.E. Podotak: Develop ment and Evaluation of an Ammonia Dosimeter. Am. Ind. Hyg Assoc J. 39 749-753 (1978) 24 Kring, E.V., W.J. Lautenberger, W.B. Baker, J.J. Douglas: A New Passive Colorimetric Air Monitoring Badge System for Ammonia. Sulfur Dioxide, and Nitrogen Dioxide. Am. Ind Hyg Assoc. J 42.373-381 (1981). 25. ACGIH: Threshold Limit Values for Chemical Substances and Physical Agents in the Workroom Environment with Intended Changes tor I98f. American Conference of Govern mental Industrial Hygienists, Cincinnati (1981). 26 DuPont: PRO-TEK Colorimetric Air Monitoring Badge Sys tem Laboratory Validation Report. Ammonia Badge, Type C-10 E I. DuPont de Nemours and Company, Wilmington, DE (1981). 27 Shor, R.M. and L.W. Anders: Direct Read Carbon Monoxide Monitor Performance Under Possible Use Conditions. Pres entation at American Industrial Hygiene Conference, Portland, OR (May 25-29. 1981) 28 Hardy, J.K., P.K. Dasgupta, K.D. Retainer, and P.W. West: A Personal Chlorine Monitor Utilizing Permeation Sampling Env Sci Tech. /3 1090-1093 (1979), 29. Moleculon Research Corp.: PROPLASTIC Chlorine Vapor Badge Information, Cambridge, MA 30. Hardy, J.K., D.T. Strecker, C.P. Savariar and P.W. West: A Method for the Personal Monitoring of Hydrogen Sulfide Using Personal Sampling Am. Ind. Hyg Assoc J. 42.283- 286(1981) 31 Graedel. T.E. and J.P. Franey: Gaseous Hydrigen Sulfide Determination by Discoloration of Lead-Stabilized PVC Am Ind Hyg Assoc J 47.947-953(1979) 3M 001511 Am Inet Hyg Asioc J (A3) August 198? 32 McCammon. C.S. and J.W. Woodfin: An Evaluation of Passive Monitor for Mercury Vapor. Am. Ind. Hyg. Assoc. J. 38 378-386 0977) 33 McCammon. C.S.. S.L. Edwards, R.D. Hull. WJ. Woodfin: A Comparison of Four Personal Sampling Methods for the Determination of Mercury Vapor. Am. Ind. Hyg Assoc. J. 41 528 531 0980) 34 Cohen. H.J.. R.K. Zahray, A.C. Misiaszek and H.J. Muranko: A New Passive Dosimeter for Mercury Presentation at American Industrial Hygiene Conference. Portland. OR (May 25-29 1981) 35 Palmes. E.D., A.F. Gunnison. J. DiMattioand C.Tomczyk: Personal Sampler for Nitrogen Dioxide. Am. Ind Hyg. Assoc. J 37 570-577(1976) 36 McMahon. R., T. Klinger. B. Ferber and G. Schnakenberg: New Technology lor Personal Sampling of NO- and NO\ in the Workplace Presentation at American Chemical Society Exposition Symposium, Las Vegas. NV (August 25-28.1980) 37 DuPont. PRO-TEK Colorimetric Air Monitoring Badge Sys tem Laboratory Validation Report. Nitrogen Dioxide Badge. TypeC-30 El DuPont de Nemours and Company, Wilmington, DE (1981) 38 DuPont: PRO-TEK Colorimetric Air Monitoring Badge Sys tem Laboratory Validation Report. Sulfur Dioxide Badge. TypeC-20 El DuPont de Nemours and Company. Wilmington, DE (1981). 39 Silverstein. L.G.: Validation of Abcor GASBADGE for Acrylo nitrile and Improved Desorption Efficiency Am Ind. Hyg Assoc. J. 38 41 2-413 (1977) 40. Hirayama. T, and M. Ikeda: Applicability of Activated Car bon Felt to the Dosimetry of Solvent Vapor Mixture. Am Ind Hyg Assoc. J 40 1091-1095 (1979) 41 Halliday. M.M. and J. Anderson; Determination of Halothane in Operating Theatre Air by Using a Passive Organic Vapor Dosimeter The Analyst 10S 289-292 (1980) 42 Evans. P.R. and S.W. Horstman: Desorption Efficiency Determination Methods for Styrene Using Charcoal Tubes and Passive Monitors Am Ind Hyg Assoc J 42 471476(1981) 43 Anders, L.W. and H.E. Mullins: Comparison of Diffusions! Organic Vapor Monitors with Charcoal Tubes for Sampling Laboratory Challenges to Contaminant Mixtures Presenta tion at American Industrial Hygiene Conference. Portland. OR (May 25 29, 1981) 44 Mazur, J.F.. G.E. Podolsk. G.G. Esposito. D-S. Rinehart and R.E. Glenn: Evaluation of a Passive Dosimeter for Col lection of 2-Bromo-2-Chloro-1.1.1-Tnfluoroethane and 2Chloro-1.1,2-Trifluoroethyl Difluoromethyl Ether. Am. Ind. Hyg. Assoc J 41 317 321 (1980) 45 DuPont; PRO-TEK Organic Vapor Air Monitoring Badges Laboratory Validation Proiocol for Diffusion-Type Air Moni toring Badges with Solid Solvents. E.l DuPont de Nemours and Company, Wilmington, DE (1981) 46, DuPont: Laboratory and Field Validation Report for PRO-TEK G-BB Diffusion-Type Badges for Monitoring Benzene Vapors. E I DuPont de Nemours and Company, Wilmington, DE (1981) 47. 3M Company: #3520 Organic Vapor Monitor with Backup Section. St. Paul. MN 48. Mazur, J.F.. D.S. Rinehart, G.G. Esposito and G.E. Podolak: Evaluation of Passive Dosimeters for Assessing Vapor Degreaser Emissions Am Ind. Hyg Assoc J. 42 752756(1981) 49. Nelms. L.H., K.D. Reiszner and P.W. West: Personal Vinyl Chloride Monitoring Device with Permeation Technique for Sampling Anal Chem.49 994-998(1977) 50. Bailey, A. and P.A. Hollingdale-Smith: A Personal Diffu sion Sampler for Evaluating Time Weighted Exposure to Organic Gases and Vapors Ann. Occup. Hyg 20 345356(1977). 51. Benson, G.B. and G.E. Boyce: A Thermally-Desorbable Passive Dosimeter for Personal Monitoring of Acrylonitrile Ann Occup Hyg 24:55-75(1981) 52. Campbell, J.E. and R.B. Konzen: The Development of a Passive Dosimeter for Aniline Vapors Am. Ind Hyg Assoc J 41 180-184(1980). 53. Mullins. H.E. and L.W. Anders: A New Innovative Diffu sions! Monitor for Sampling Ethylene Oxide in Air Presenta tion at American Industrial Hygiene Conference. Portland. OR (May 25-29. 1981) 54 Rodriguez. S.T., P.B. Olson and V.R. Lund: Colorimetric Analysis of Formaldehyde Collected on a Diffusional Moni tor. Presentation at American Industrial Hygiene Confer ence. Portland. OR (May 25-29, 1981). 55 DuPont: PRO-TEK Colorimetric Air Monitoring Badge Sys tem Laboratory Validation Report, Formaldehyde Badge, Ser ies II. Type C-60 E I DuPont de Nemours and Company. Wilmington, DE (1981) 56. Kriesel. R.S.: Formaldehyde Vapor Detection-- New Sam pling Technology. Presentation at American Industrial Hygiene Conference, Portland, Or (May 25-29. 1981). 57. Matherne. R.N.. P.L. Lubs and E-J- Kerfoot. The Develop ment of a Passive Dosimeter for Immediate Assessment of Phosgene Exposures Am Ind Hyg. Assoc. J 42 681684(1981) 58 Hill, R.H. and D.A. Fraser: Passive Dosimetry Using Detec tor Tubes. Am. Ind. Hyg. Assoc. J 41 721 -729 (1980) 59. Jones, W., E.D. Palmes, C.Tomczykand M. Millson: Field Comparison of Two Methods for Determination of NO. Con centrations in Air, Am. Ind. Hyg. Assoc. J. 40 437438(1979) 60 Evans. M., M. Molyneux. T. Sharp, A. Bailey and P. Hollingdale-Smith: The Practical Application of the Potion Diffusion Sampler for the Measurement of Time Weighted Average Exposure to Volatile Organic Substances in Air. Ann. Occup. Hyg 20 357-363 (1977) 61. Zaebst, D.D., M.F. Boenigerand J.R. Burg: Field Compari son of Two Passive Organic Vapor Sampling Devices to the Charcoal Tube Presentation at American Industrial Hygiene Conference. Houston, TX (May 18-29, 1980) 62. McKee, E.S., P.W. McConnaughey and I.M. Pritts: Colori metric Personal Dosimeters for Some Inorganic Contami nants. Mine Safety Appliances Co . Pittsburgh, PA 29 December, 1981: Revised 8 February. 1982 Amencan Industrial Hygitnr Association JOURNAL (43) S 62 3 0015)2 G2J LITERATURE REFERENCE page 1 , " PCROPLASTIC SORBENT TJBE ", TECH CORP .CAMBRIDGE. MA , I960 INFO. FROM MOLECULAR RESEARCH ANONYMOUS , 21 , 1979 " MONITOR WORKER EXPOSURE TO GASES ", CHEM ENG. NEWS P. BAILEY, A & F A HOLLINCDALE-SMITH , " A PERSONAL DIFFUSION SAMPLER FOR EVALUATING TIME WEIGHTED EXPOSURE TO ORGANIC GASES AND VAPORS ", ANN OCCUPA. HYG 20 345-356 , 1977 BAMBERGER, R.L. G G. ESPOSITO, B V JACOBS, G.E. PODOLAK AND J.F. MAZUR , " A NEW PERSONAL SAMPLER FOR ORGANIC VAPORS ", AM IND. HYG. ASSOC. J 39 701 , 1978 BELL, DR., K.D. REISZNER AND P W WEST , " A PERMEATION METHOD FOR THE DETERMINATION OF AVERAGE CONCENTRATIONS OF CARBON MONOXIDE IN THE ATMOSPHERE ", ANAL, CHEM, ACTA 77 255-262 , 1975 BELL, D R , REISZNER, K D , AND WEST, P.W. , " A PERMEATION METHOD FOR THE DETERMINATION OF AVERAGE CONCENTRATIONS OF CARBON MONOXIDE IN THE ATMOSPHERE ", ANAL CHIM ACTA 77, 245 , 1975 BRAUN,' D.L , " GAS DETECTION DEVICE ", US PATENT, 3,3924,219 , 1975 BRAUN, D L " DETECTION OF MERCURY VAPORS AS AN ADJUST TO RESPIRATORY PROTECTIVE DEVICES ", PRESENTED AT A1 HA ANNUAL MEETING, SAN FRANCISCO, CA , 1972 BROWN, R H. AND WALKING. K.T , " THE PERFORMANCE OF TUBE-TYPE DIFFUSIVE SAMPLER FOR ORGANIC VAPCURS ", AMERICAN INDUSTRIAL HYGIENE CONFERENCE, HOUSTON, TX , 1980 EROWN, R H , CHARLTON, J AND SAUNDERS, K J AN IMPROVED DIFFUSIVE SAMPLER ", AM IND HYG 198 1 " THE DEVELOPMENT OF ASSOC.. J. 42, 865 , CAMFBELL, J E AND KQNZEN, R.B , " THE DEVELOPMENT OF A PASSIVE DOSIMETER FOR AIRBORNE ANILINE VAPORS ". AM IND HYG ASSOC. J. 41, 180 , 1980 D'AGOSTINO, R B AMD J C GILLESPIE , " COMMENTS ON THE OSHA ACCURACY OF MEASUREMENT REQUIREMENT FOR MONITORING EMPLOYEE EXPOSURE TO BENZENE. ", AM. IND. HYG ASSOC, J 3 51 0 - 5 1 3 , 1978 EVANS, M , M MOLYNEUX, T SHARP, A BAS! LEY AND *> HOL LINGDAL E-SMITH , " THE PRACTICAL APPLICATION OF THE PORTON DIFFUSION SAMPLER FOR THE MEASUREMENT OF TIME WEIGHTED AVERAGE EXPOSURE TO VOLATILE ORGANIC SUBSTANCES IN AIR ", ANN OCCUF HYG 20 357-363 , 1977 FERBEH, B I , F A SHARP AND R W FREEDMAN , OF NITROGEN ", U.S. PATENT 3,992, 153 , l'H " DOSIMETER FOR OXIDES GONZALEZ, L , " PH D THESIS (IN F R 0 C E S 3 ' ", DEPT. OF CHEM. ENG. 6 APPLIED CHEMISTRY, U OF TORONTO , GOSSELINK, D.W , D L BRAUN, H E MULLINS AND S T. RODRICUEZ , " A NEW PERSONAL ORGANIC 7AFCR MONITOR WITH IN-SITU SAMPLE ELUTION ", 3M 3M 001513 page 2 CO TECH BROCHURE, < RE PR 1 NT OF PAPER PRESENTED AT A1 HA ME , 1978 HARDY, J.K , DT STRECKER , C ? SAVARIAR AMD P . W WEST , " A METHOD FOR THE PERSONAL MONITORING OF HYDROGEN SULFIDE USING PERMEATION SAMPLING ", AM IND HYC ASSOC J -I 2 ; 2 ) 2 12,-266 , 1981 HARDY, J K , PK DASGUPTA, K D REI5ZNER AND P W WEST , " A PERSONAL CHLORINE MONITOR UTILIZING FERMEATIOM SAMPLING ", ENVIRON. SCI TECH 13 10 90-,0 . 1979 HARRISON, J.W., LAWLESS, P A , RESEARCH TRIANGLE INSTITUTE , DOSIMETRY ", EPA ' ESRL ' REPORT 1976 GILBERT, D E., AND WHITE, J H., " DEVELOPMENT STRATEGY FOR POLLUTANT E F A - 6 J 0 / 2 - 6 - 034, NTIS PB-265-910 , HEARL, F J AND MANNING, M P '* TRANSIENT RESPONSE OF DIFFUSION DOSIMETERS ", AM IND HYG ASSOC J 778 , 1980 HILL, R.H AND DA FRASER , " PASSIVE DOSIMETRY USING DETECTOR TUBES " , AM IND. HYG ASSOC J 41<10> 721-729 , 1980 JONES, L C., BILLINGS, Z E., AND LILIS, C , " LABORATORY PERFORMANCE OF PASSIVE PERSONAL SAMPLERS FOR WASTE ANESTHETIC GAS (ENFLURANE) CONCENTRATIONS ", AM. IND HYG ASSOC J 42, 104 , 1981 KAVANAGH, S., S L MILLER, J. SEAL, A J. STEVENS, J SWALE AND DA REAVELEY , " AN EVALUATION OF THE PORTON DIFFUSION SAMPLER FOR LONG-TERM MONITORING OF HAL07HANE VAPOUR CONCENTRATIONS ", AM OCCUP. HYG. 23:133-146 , 1980 KRING, E.V , HOFFMAN , " FOR AMMONIA, ASSOC. J. 42 W J LAUTENBERGER, W B BAKER, J.J DOUGLAS AND A NEW PASSIVE COLORIMETRIC AIR MONITORING BADGE SULFUR DIOXIDE AND NITROGEN DIOXIDE ", AM. IND. 373-381 , 1981 R A. SYSTEM HYG. LAUTENBERGER, W J , E.V KRING AND J A. BADGE MONITOR FOR ORGANIC VAPORS ", AM 41(10),737-747 , 1980 MOREL LG , IND HYC. " A NEW PERSONAL ASSOC J LUGG, G A. , " DIFFUSION COEFFICIENTS OF SOME ORGANIC AND OTHER VAPOR IN AIR ", ANAL. CHEM 40 ;07Z , .968 MATHERNE, R N , PL. LUB3 AND E.S KERFOOT , " THE DEVELOPMENT OF A PASSIVE DOSIMETER FOR IMMEDIATE ASSESSMENT OF PHOSGENE EXPOSURES ", AM. IND. HYG. ASSOC. J 42:681-684 , 1981 MAZUR, J.F , D.S RINEHART, C G ESPOSITO, AND G.E PODOLAK , EVALUATION OF PASSIVE MONITORS FOR ASSESSING VAPOR DEGREASER EMISSIONS ", AIHA JOURNAL 42, 752-756 , 1981 MAZUR, J F , G.E PODOLAK, AND B T HEITKE , " USE OF A GC CONCENTRATOR TO IMPROVE ANALYSIS OF LOW LEVELS OF AIRBORNE HYDRAZINE AND UNSYMMETRICAL DIMETHYLHYDRAZINE " AI HA JOURNAL, 4 1, 6 6 -69 , 1 980 MAZUR, J F , G E PODOLAK, G.C ESPOSITO, D S RINEHART, AND RE GLENN , " EVALUATION OF A PASSIVE DOSIMETER FOR COLLECTION OF 2-BROMQ- 2-CHLORO-l , 1 , 1 . -TR1FLUOROETHANE AND Z-CHLORO-1 ,2,-TRIFLUOROETHYL DIFLUOROMETHYL ETHER IN HOSPITAL OPERATING ROOMS ", AI HA JOURNAL, 41,317-321,1980 3M 001514 page 3 MAZUR, J F . , R L BAMBERGER, G E PODOLAK, AMD G G. ESPOSITO , DEVELOPMENT AND EVALUATION OF AN AMMONIA DOSIMETER ", AI HA JOURNAL, 3?, 749-753 , 1978 MC CAMMQN, C.S AND J W. VOODFIN , " AN EVALUATION OF A PASSIVE MONITOR FOR MERCURY VAPOR ', AM IND HYG ASSOC J 38 378-386 1977 , MC DERMOTT, D .L , K D RE I SZNER AND F W WEST , " DEVELOPMENT OF LONG-TERM SULFUR DIOXIDE MONITOR USING PERMEATION SAMPLING. ", ENVIR. SCI. AND TECH 13 1087-1090 . 1979 MONTALVO, J G , JR , ' TOTAL ELEMENTAL CONTENT PASSIVE PERSONAL MONITORS. ", AM IND HYG ASSOC J 40:1046-1054 , 1979 MULLINS, HE AND L W ANDERS MONITOR FOR SAMFLING ETHYLENE ( IN PRESS > , , " A NET INNOVATIVE DIFFUSIONAL OXIDE IN AIR ", AM IND. HYG. ASSOC. J. NADEAU, J S. AND D G.B EOOCOCK , " STABLE FREE RADICAL REAGENT AND SOLID PHASE SUITABLE FOR A NITRIC OXIDE DOSIMETER ", ANAL. CHE. 4? 1 6 72- 1 6 76 , 1 97 7 NADEAU, J S , M.E TREEN AND O.G B BOOCOCK , " MASS TRANSFER EFFECTS IN A NITRIC OXIDE DOSIMETER. ", ANAL CHEM 50 1 87 1 - 1 87 3 , 1 978 NELMS, L H , K D RE ISZNER AND P W VEST , " PERSONAL VINYL CHLORIDE MONITORING DEVICE WITH PERMEATION TECHNIQUE FOR SAMPLING. ", ANAL. CHEM 49 ? 4 - 9 9 8 , 1977 OROFINO, T A AND A M USMANI , JULY 96-104 , 1980 " FASSIVE DOSIMETRY ", AM. LAB PALMES, ED A F GUNNISIN, J DI MATT IO AND C TOMCZYK , " PERSONAL SAMPLER FOR NITROGEN DIOXIDE ", AM IND. HYG ASSOC J. 37:570-577 , 1976 PALMES, ED AND R H LINDENEOOM . " GHM1S LAW, FICK'S LAW AND DIFFUSION SAMPLERS FOR GASES ", ANAL CHEM 51 2400-2401 , 1979 PALMES, SAMPLER 19 7 6 E D , A F GUNNISON, J D MATT 1G AND C, TOMZYK , " PERSONAL FOR NITROGEN DIOXIDE", AM INO HYG ASSOC J 37.570-577 , PODOLAK, G E , R M MC KENS IE, D S RINEHART, AND J F MAZUR , " A RAPID TECHNIQUE FOR COLLECTION AND ANALYSIS OF PHENOL VAPORS ", AIHA JOURNAL, 42, 734-738 , 1781 PROCEDDINGS OF AN ACGIH TOFICAL SYMPOSIUM, CINCINNATI, OHIO , DOSIMETRY FOR CHEMICAL AND PHYSICAL AGENTS " 1 , 1980 PURNELL, C.J , WRIGHT M T , AND BROWN, R H " PERFORMANCE OF THE FQRTON DOWN CHARCOAL CLOTH DIFFUSIVE SAMPLER ", ANALYST 106, 590 , 198 1 RE ISZNER, K.D AND P W WEST , " COLLECTION AND DETERMINATION OF SULFUR DIOXIDE INCORPORATING PERMEATON AND WEST-GAEKE PROCEDURE ", ENVIRON SCI *T"ECH 7 5 2 6 -5 3 1 1 773 RODRIGUEZ, S T , F B OLSON AN I' 7 R LUND , COL ORMETRIC ANALYSIS OF 3H 001515 page 4 FORMALDEHYDE COLLECTED ON A DIFFUSIONAL MONITOR ", AM ASSOC J (IN PRESS) , IND. HYG. SCHNAKENBERG, G . , UR ' L S eUREMJ OF MINES TECHNICAL PROGRESS REPORT 95 ", PITTSBURGH MINING AND SAFETY RESEARCH CENTER, PITTSBURGH, PA , 1976 SEFTON, M V AND C LOMBARDI , " CONTINUOUS MONITOR OF THE EXPOSURE TO INDUSTRIAL GASES AND VAPOR CONTAMINANTS ", US PATENT APPLICATION , 1980 SEFTON, M.V., A.V KOSTAS AND C LOMBARDI , " ANALYSIS OF DIFFUSION WITH IRREVERSIBLE REACTION IN A PASSIVE DOSIMETER ", PROCEEDINGS SECOND WORLD CONGRESS OF CHEMICAL ENG MONTREAL , 1981 SEFTON, MV , EL. MASTRACCJ AND U L MANN , " RUBBER DISK PASSIVE MONITOR FOR BENZENE DOSIMETER ", ANAL CHEM 53 458-461 , 1981 SHOR, R.M., L W ANDERS AND R A BERNIER , ' DIRECT READ CARBON MONOXIDE MONITOR PERFORMANCE UNDER POSSIBLE USE CONDITIONS ", 3M COMPANY TECHNICAL BROCHURE , SILVERSTEIN, LG., " VALIDATION OF AECOR "GAS-BADGE" FOR ACRYLONITRILE AND IMPROVED DESORPTION EFFICIENCY ", AM IND ASSOC J. 38 412-413 , 1977 HYG STEPHENSON, K A , " PASSIVE MONITORING DEVICES FOR ANALYSIS OF BENZENE AND CARBON DISULFIDE ", UBTL DIV , UN. OF UTAH RESEARCH INSTITUTE, SALT LAKE CITY,UT , 1979 TOMPKINS, F C., UR AND R L. GOLDSMITH , " A NEW PERSONAL DOSIMETER FOR THE MONITORING OF INDUSTRIAL POLLUTANTS ", AM IND HYG ASSOC. . J . 38371-377, 1977 TOSHIKO, H AND M IKEDA , " APPLICABILITY OF ACTIVATED CARBON FELT TO THE DOSIMETRY OF SOLVENT VAPOR MIXTURE ", AM. IND HYG ASSOC J 40 1091-1096 , 1979 WEST, P.W AND K D REISZNER , " FIELD TESTS OF PERMEATION-TYPE PERSONAL MONITOR FOR VINYL CHLORIDE ", AM IND HYG. ASSOC. U. 39 645-650 . 1978 WILLIAMS, K E , AND J F MAZUR , " GAS CHROMATOGRAPHIC ANALYSIS OF ACETIC ACID IN AIR ", AI HA JOURNAL, 41, 1-4 , 1980 3M 001516