Document 6R1MadvVeJxXaE3Gry9NKMwMm

Am Ind Hyg Assoc J 43(8) 605-621 (19821 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 VERNON E ROSE and JIMMY L PERKINS School of Public Health. University of Alabama m Birmingham, Birmingham, AL 35294 introduction Recognition, evaluation and control arc the cornerstones of the application ol that mixture ol science and art known as ind us trial hy gicne. These three tasks, how e\ er. 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 training of indiv iduals highly special ized m the control of specific hazards, especially those involving noise and toxic air contaminants These dev elopments are welcomed because they contribute significantly to the ultimate goal of pmtecting the health of workers by providing safer and more healthful workplaces. Ai 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 w here 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 the determination of worker exposure to airborne toxic substances, the industrial hvgienist has seen a rev olution in the development of sophis ticated techniques and equipment. The "organ-grinder" impinger sampler is a relic, having been replaced bv constant flow. eight-hour battery-operated pumps, light enough to be carried by the worker. The liquid bubbler and impinger have been replaced by the charcoal and chemical substrate sampling tube.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 directlv 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 dev ice has appeared w hich has the key of simplicity -- the personal passiv e dosimeter: personal, because il can he w orn 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 w ith the term dosimeter, vv uh purists preferring to call them collectors, monitors, or samplers. While many of the devices are collectors and require iheapplication of subsequent analytical procedures, others prov ide for a more direct measurement of "exposure dose." Their basic appeal, however, is simplicity ol use Theoretically. elaborate calibration procedures are 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 adv ise 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 dosimeters 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 matcnals can provide a quantum leap in our ability to provide sale and healthful workplaces. With any sampling dev ice. however, there also must be the understanding that use ol such dev ices is only one part of the evaluation step The concepts of proper selection of workers at risk: the understanding of limitations, interferences and similar factors: and tilt imately the proper interpretation of the results ate still key ingre dients in the evaluation step. 1 he possibility of "false nega tive" decisions leading to erroneous assumptions ol safely. or "false positive" conclusions leading to unwarranted expenditures of resources lor eontioK. still exists regardless of the measurement device used American Industrial Hyg'ene Association JOURNAL Copy's*1' 1982 America? Industrial Hyp,PHY Assooftipr (43) ? 62 ^_ 3M 009929 60b 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 lorcesare relied upon to ensure that a representative amount of contaminant is "seen" by the detector. To date, one of two principles has been applied in the design of dosimeters. The first, and most widely used, is the principle of diffusion of contaminant molecules through a stagnant gas (air) layer. The second principle inv olves the absorption in and subsequent permeation of contaminant molecules through a membrane. Diflusional monitors rely on the movement ol contami nant molecules across a concentration gradient which for steady-state conditions, can be defined bv Tick's Tirst l aw of Diffusion 111 \\ = -PA^ d\ (1) where. W =- mass transfer rate, ng sec. D -- diffusion coefficient, cm- sec. A = cross sectional area of diffusion path, cm', and dc d\ ~ the instantaneous rate of change in concentra tion over diffusion path, (ng cm'V'm \ Considering the change in concentration (Ci -- Cu) over the total diltusion path length (Xi -- X,. -- --I ), equation (1) becomes: W = D y-(C, - C,,) (2) where. 1. = length of the diffusion (static) path, cm, Ci = ambient concentration of contaminant, ng cm', and C. = concentration of contaminant at collecting sur face. ng cm'1. II an effective collection medium is employed, the contam inant concentration at the surf ace of the collector (Co) can be assumed to be zero, and multiply ing both sides of equation (2) by time, y iclds M = DytC.li (3) where: M = total mass transferred, ng. and t -- time that the badge is exposed to the contami nated an. sec. It is also interesting to note that the units of the product of D and A, div ided by T.arecnv sec. w hich are the same units associated with active air-mov ing dev ices such as personal sampling pumps. Rearranging equation (3) as follows: Ml C DAt (4) it becomes apparent that live factors affect the measurement of the ambient air concentration of a substance (C i). 1 wo ol the factors (L and A) arc physical parameters associated with the construction of the dosimeter, one ( M) is prov ided bv measuring the total mass of contaminant collected by the sampler, another is the duration (t) the sampler was exposed to the contaminated atmosphere, and the final factor (Di is an individual property of each vapor or gas. It also is known1'1 that the diffusion coefficient is directly propoitional to the absolute temperature (T) of the vapor, raised to three-halv es power and inverscly proportional to the atmo spheric pressure (P), Do <5| Dosimeters that rely on the principle of permeation through a membrane are especially use! ul w here the contam inant of concern is usually found mixed w itli other interlei ing vapors or gases or when a liquid collecting medium is employed. The goal then becomes to identify a membrane material that is highly permeable to the contaminant ol interest and impermeable to most other components in the atmosphere, and or the collecting media. The determination of ambient concentrations of a con taminant using a permeation device can be determined Iron the formula: C = wk i (6) where: C = concentration of contaminant, ppm. w = mass ol contaminant collected, gig, k = permeation constant, ppm-hours pe. and t r exposure time, hours. The permeation constant (k) is determined experimentally and is a function of the specific membrane material and contaminant ol 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 the 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.131 Montatvohasdescribed a procedure for limiting errors associated w ith computed diffusion coefficients.I't' At 3M 009930606 Am Ind Hy Assoc J (43) August l9fiT least one manufacturer, the 3M Company, makes available its procedures for determining sampling rates ( DA L) for its badges. " Itsapproach has been to experimentallydetermine the sampling rate fot five 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 empit ical relationships developed from the test compounds The rationale for the selection of the Hirschfelder equation is not given, but in the study of the nine diffusion coefficient foimulas. the author concluded that for higher molecular weight compounds the Hirschfelder. Hiard and Spat/ equa tions were in closest agreement with determined values.13' hoi the petmeation monitor, accurate determination o! ihc permeation coefficient for each monitor is necessarv for obtaining accurate results. Factors influencing permeation include, thickness and uniformity of the membrane, affinitv o! the membrane for the anal y tc. swelling or shrinkage of the incmbianc, and possible etching by corrosive chemicals. 1 he pi oblenrs associated w uh accurate determinations ol the mass ol the contaminant collected arc similat to those involved with other collection devices such as charcoal or silica gel tubes, or to those in which the collection of the contaminant inv olves 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 analv tical techniques are also pai t of the total ei rot associated w uh the measurement. Another common concern in all tv pcs 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, e.g.. effects on adsorption or ab'-otption efficient's ol the sampling medium, chemical reactions ol two or more contaminants prior to analv sis. and the multitude of interferences associated with analysis of complex mixtures of gases and or vapors. These problems also are found in the more classical sampling and analyti cal 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 effect on v ariabilitv. These factors are the tw o already identi fied, temperature and pressure, and. less readily apparent, the velocity of the air external to the badges. Considering temperature and pressure, and referring to equation (5) it can be shown that a temperature rise from 5 to 35 C would give a 16 percent increase in the diffusion coefficient, while a rise in harometnc pressure trom 710 to 8 10 mm Fig would cause a 14 percent decrease '' Howcvet. 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. As a result, the total mass (M) collected by the dosimeter is only slightly aflected by temperature |M"1"I and is independent of the pressure "'Consequently. w bile at ambient temperatures, the diffusion coefficient will increase about 0,5 percent per C, and the total mass collected hv tfu sampler w ill increase less than 0.2 percent per 0 C 1 he ret ot e. a temperature change Irom 25 to 30 C, if uncot reeled, will introduce a measurement error of less than one percent, while a change from 5 to 35 C. il uncorrected, would introduce an error of about five percent. The final source of error to consider is the velocity ol the air external to the dosimeter: often this is referred to av face v elocity. 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."1 As Jonas el at. subsequently noted, the lace velocity directly a fleets the concentration gradient Ci --C> in equation (2). and C'i can no longer be assumed to be the ambient concentration w hen the air external to the badge i' stagnant l6' With zero or low face velocities, the length 11 (of the diffusion pathway is effectively extended, and there is a decrease in the measured ambient concentration In Tompkins'and Goldsmith's work with the GASBAlXir". they determined experimentally that as long as lace veloci ties were greater than 7.5 cm sec (15 fpm) there wax "no significant eflcct on dosimeter response:" however, experi mental results supporting this conclusion were not pre sented."1 High face velocities may also affect the coneennation gradient. Commercially available diffusion device' rely on cither a large ratio ol diffusion path length to diffu sion tube diameter or a wind screen to limn error' Irom this condition. One of the most comprehensive tests todocumem source' oferrorhas been conducted under contract forthe National Institute for Occupational Safetv and Health, and although concluded, it is not yet available as a public report The study involved evaluation of the GASBMXif and 3M Organic Vapor Monitor"' (the DuPont badge not being available at the time the study was initiated) via challenge with several organic vapors. The lactors investigated were precision, effects of storage, maximum and minimum levels of quantification, face v elocity cl feet', effect' ol temperat ure and humidity, ofl-gassing (related to 'image). exposure to mixtures, problems associated with applicable analytical methods, and adsoipuon ol the contaminant by the badge itself with subsequent leaching lo the sensing surlacc The possibility of adsorption by the badge body, thus giving Amer/car Industrial Hyfipnp Association JOURNAL (43) 6 2 3M 009931 r higher results if the contaminant is subsequently released to the active medium, is of special concern in using passive dosimeters to measure very low ambient concentrations such as might be found in air pollution studies. Such interest and concern arc ev idcnced by research on the subject being sponsored by the U.S. Environmental Protection Agency (EPA).'#I Because of the lower concentrations involved with air pollution studies as opposed to workplace environments, the EPA also is concerned with the background or postmanufacture contamination lev els associated with the sens ing medium. Initially . the focus concerns organics and acti\ated charcoal. In summary, although numerous factors may affect the linul calculation ot concentration, only face velocity and the determination ol the dillusion coefficient are unique sources ol error for passive collectors Therefore, if face velocities arc sufficient to prevent "starvation"(probably greater than 7.5 cm see) and if diffusion coefficients have been accurately calculated or experimentally determined, passive dosimeters should giv e 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 . esults of these tests requires the application of appropriate statistical techniques. The use of statistical techniques w hich 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 0 both field and laboratory validation data. The main diference between the tw o situations is the degree of certainty of the "true" concentration of the monitored environment. 1 n the field, the true value is usually an estimate based on the esults of a standard sampling and analytical method In the laboratory, experimental "known"concentrations 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 "known" concentrations. These errors are often difficult to estimate. The "known" concentration is often calculated by weighing a syringe before and after an injection period (mass lalance) or simply by injecting or allowing to diffuse a Treasured volume. It is assumed that the aliquot delivered vas vaporized or diffused into a test chamber of known size. Possible sources of error include adsorption to or leaks from .he 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 m measuring the injected contaminant. A backup monitor ing system may be used to ensure close proximity to the `k now n" concent rat ion. For example, an infra-red (lR)anay/cr or gas chromatograph may be used as a check on a known" concentration In other instances an 1R analyzer or a direct reading instrument may be the only method fordetermining"known" 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 thv estimated concentration are considered, statistical tests used to validate the experimental method become considerably more complicated: hence, the error in measuring the "known" concentration is usually assumed to be small and unimpor tant. Methods described above for determinint the "know n" concentration vary in their accuracy, a fact which should he considered when 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 ot data points about their mean, and the dev iation of the sam ple mean from the true mean or "known"concentranon. The first consideration often is called precision and is probahlv the most important and reliable measure as it does not depend on the error in determining the "known"coneentration. Precision is estimated by determining the coefficient ol variation (CV) or relative standard deviation of the data set as follows: CV = " X 100 A (7) where: s = Standard deviation of sample data set, and X = Mean of sample data set. Where samples are taken at several concentrations, it is necessary to determine a pooled coefficient of variation which involves determination of number of levels tested.'101 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 w hile 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 100 Xf) (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.1111 r>08 Am Ind Hyp Assoc J (43) August 198? 3H 009932 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 indiv idual samples or the levels) are consistently negative or positive. If the bias is large and varies consis tently 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 systematicas opposed to random error), causing the experimental values to con stantly fall short or long of the "known "concent rat ion. 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 sy stem accuracy1111 has been defined as (2 X CV) T- absolute bias, expressed as a percent. Others1121 have used the percent age of the "known" concentration accounted for by the sample mean two standard deviations as well as the term systematic error11'1 Ml which is equivalent to overall system accuracy. Relative standard deviation has also been used, and is defined as the equivalent of CV.11'" 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 ow n 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.K percent) is the maximum precision value acceptable for an unbiased method Although the 25 percent accuracy criterion has been criticized by some authors,111 ' it was adopted for NI OS H -s ow n internal use and is not meant as public policy . However. OSH A adopted the same criterion for the benzene standard, w ithout a complete derivation or explanation. Consequently, this criterion has been criticised and alternatives have been proposed.11'1 A second important point is that bias is also considered in the 25 percent criterion according to a somewhat complex statistical relationship,111'1 but the overall system accuracy as defined earlier1111 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 deviation and CV should decrease These considerations are important w hen evaluating passive monitor validation data, especially in those cases where manufacturers have stated that thev 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 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 he on the regression line, the correlation coefficient (r) w ould have 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 tw o devices are indeed equiva 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, w e know and can calculate under laboratory conditions the error of active sampling systems There are at least three reasons why this error is olten 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;1181 however, the the ories apparently have not been applied to sampling and analytical methods even though their appropriateness has been recognized.118' 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.<`pl Their gas detector for carbon monoxide involved 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 w ith the carbon monox ide on the light colored absorbent material. This type ol semiquantiiative device was certainly a forerunner ol 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 Plant/ cl a!, to develop a personal dosimeter for measuring hy drazine, unxymmeirical dimcthylhydra7ine and monomethylhydrazine.1'11 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 met hod was only semi quantitative. In considering sources of error the authors noted that the purple color would also be produced by all volatile bases that were tested, including ammonia, aliphatic amines, aniline and cigarette smoke American induMnai Hygiene Association JOURNAL (43) 8 `8? 3M 009933 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 de\ ice to be reported in the literature was described bv Palmes and Gunnison in 1973 1221 Their device employed the principle of gas diffusion to determine airborne concentra tions of sulfur dioxide and w ill receive further consideration subsequent Iv To gain the best overs iew of the \ arious appli cations of these concepts, it is probabls best to proceed b> considering first the inorganic and then organic gases and \apors. inorganic gases and vapors ammonia In 1978, Ma/ur ci at. described the use of the Abcor GASBADGE to sample employee exposure to ammonia (this dewcc current!) is not marketed).1"1' The investigators replaced thecharcoal pad normal!) found m the GASBADGE uith an acid impregnated absorption pad. Of three acids tested, phosphoric was most successful in pros iding the best approximation ol theoretical concentrations. Thev deter mined. howe\ ci. that \ olatile amines, specificallv cyclohcxv 1amine. could produce high readings, as high as 185 percent ol the svnthctic atmosphere. This led them to replace the glass fiber draft shield on the front of the GASBADGE with a "charcoal impregnated glass fiber filter which had been pretrealed with alcoholic KOE1 containing 0.1 percent sur factant. " 1 he chatcoal served to adsorb amines as they dif fused into the dosimeter, while the KOH (aided bv the wetting agent) eliminated irreversible ammonia adsorption bv the charcoal, which would have caused underestimation of the ambient concentration Additional laboratory exper iments demonstrated that storage time of up to 47 davs. pi ior to anal) sis. did not appear to adv erselv affect the results. More recenilv. DuPont has developed a commercially available svstem for the measurement of several airborne contaminants including ammonia. In 19H1, Kring ei at. described DuPont's PRO-TEKT"systemforammonia. nitro gen dioxide and suit ur dioxide sampling analysis using a col orimetric readout instrument '"v The ammonia badge relies on moleculai diffusion of ammonia and subsequent chemical reaction w ith a solution of 0.3N boric acid and 0.03TX sodium potassium tartaratc (mV). After exposure, the reagent pack is removed from the badge holder and analvsis is initiated by pressing reagent "blisters" w hich are adjacent to the absorb ing solution This action causes the release of a modified Nessler's reagent and the subsequent development of a colored solution. For ammonia, maximum color intensity is developed at 425 nanometers. The absorbance of the sample is then compared against a standard curve based on Beer's Eaw After determination of the precision of the analytical method and verification of the linear range of the color chenustrv. laboratorv testing was conduct, d to establish the operational range as well as precision and accuracv of the overall method (see Tabic 1). The minumum and maximum limits of the sampling range were found to be 50 and 500 ppm-hours. respective!). E'or an eight-hour time weighted average, these values correspond to one-fourth and twoand one-half times thecurrent ACG1H Threshold Eimit Value of 25 parts per million.In considering sources of error, env ironmental effects including temperature (10 to 40 C). relative humiditv (I0to80 percent). pressurc(730 to 790 mm Hg), and face vclocitv (2.5 to 125 cm sec) were included. Of the env ironmental factors evaluated, temperature and the concentration of the contaminant were identified as being responsible for 98 percent of the data variation. For ammo nia, a temperature correction factor of 0.6 percent per degree centigrade was suggested. Also investigated was the storage stabilitv of both unexposed and exposed badges Results indicated that refrigerated slot age is necessarv toextend the shelf life of unexposed badges Once the badge is exposed to ammonia and bclorc the reagents arc mixed, the badges can be stored lor one (room temperature) to three (refrigerated) weeks without losing anv absorbed contaminant Once the reagents aie mixed and color formation is started, the badge should be read w ithin 90 minutes. Additional testing results conducted bv DuPont are shown in fable I ub' carbon monoxide Shor and Anders, of the 3M Companv, have described the 3M "direct-read diffusional monitor" for evaluation ol exposures to carbon monoxide.,2,) The principle involves the reaction of the carbon monoxide and an unreported rcagent(s) to give a visible color change from pink to tan. Theoreticallv. "if any 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 summarv results of laboratorv evaluations using an infrared radiation dev ice to establish "known" concentrations (see Table I). chlorine Hard) et at. have described a personal chlorine monitor (REAE. Inc.) which employs the principle of permeation of the gaseous contaminant through a silicone membrane and into 10 ml. of a fluorescein-bromide solution.(2S| 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 graphicallv Moleculon Research Corporation has recently introduced a chlorine monitoring device which relies on plastic film impregnated with liquid reagents.<29' Exposure of the badge to chlorine gas gives a visible, "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, humiditv. w ind velocity and concen tration are reported as presenting an error at the 95 percent confidence level, which is "less than 15 percent." 610 Atr Ind Hyp Assoc J (43) Aucust 198? 3M 009934 Chemical TABLE I Inorganic Gases and Vapors Laboratory Results Dosimeter* Bias'* Precision' Range" (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 0.5 -3.2 -3 2 -0 9 -4 9 -1 -0 8 0.5 17 03 74 69 93 21 7 75 87 41 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 1 6-2.2 0 03-0 3mg/m1 O 05-0.2mg/m1 50 1830 24 26 23 1 38 24 36 1 38 24 1 32 33 27 rc Hl K f. H1 H1 E iG (. 'DP-DuPont Pro-Tek Colorimetric System Badges. 3M-3M Company Monitor. MDA=MDA Scientific, GB=Abcor GASBADGE hSee 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 et at'u` `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 develop ment of the GASBADGE personal sampler.1*1 Although later work with this device focused on the collection of organics on an activated charcoal substrate, initial studies researched sampling of both organic and inorganic com pounds. (The GASBADGE for organic vapors is now mar keted by National Mine Safety Company. and those for inorganic vapors are not currently marketed.) Applications involv 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 were within 25 percent of the "true" value. Challenge concentrations were established in a "well-mixed" environmental test chamber and were measured with an "independent wetchemistry sampling train." Hardy and associates have described a permeation device (REAL, Inc.) which relies on the permeation of H2S 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 knowledge of exposure time then allows for the determination of average exposure over the measurement period. The authors note that a critical step in American Industrial Hygiene Association JOURNAL (43) 8 82 the development of such a dev ice is the experimental deter mination of the permeation constant (see Equation 6). w hich involves calibration of each monitor by exposure to know n concentrations of the contaminant. The results of this labo ratory research demonstrated a detection limn of 0.01 ppm for an eight-hour exposure, with a working range ol 0.1 to 2l) ppm and a linear response up to 200 ppm. The working range corresponds to one one-hundredth to two times the current eight-hour TLV of 10 ppm.'251 Evaluations ol envi ronmental effects indicated that neither temperature, over the range of--3 to 39 C. nor humidity , front 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 hydro gen sulfide has been reported by Gracdel and Franey.'311 Their research involved using a semiquantitative method without a stagnant air layer and relying on the discoloration of lead-stabilized polyvinyl chloride (PN C). The technique involves the diffusion of gas in a polymer 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 009935 mercury In 1977, McCammon and Wood fin of NIOSH reported the result1- of a laboratory evaluation of 3M's mercury vapor monitor <33,The monitor's operating principle inv olves molec 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 inv olved the active movement of air, also were inves tigated and include the LASL tandum sampling tube, the hopcahte tube, and the iodine impregnated charcoal tube, For the passive monitor, precision and accuracy, the effects of face v elocity and temperature, and potential interferences were investigated Concentrations of mercury vapor in an exposure chamber were monitored w ith an ultras iolet mer cury vapor meter, which in turn was calibrated by measure ments using the 1.AS1 method. To determine precision of the monitors. 12 dev ices vv ere exposed to a test atmosphere. Results from three measurements of the test atmosphere using the LASL method gave an "expected" concentration ol 0 056 milligrams of mercury per cubic meter of atr (mg m'). with a standard deviation (SD) of 0.002 mg m3 and a coefficient of variation (CV) of 0.027. Precision and bias calculated for the data given in Table III of McCammon ei al is summarized in Table 1. A least squares regression analy sis of the combined precision and accuracy results for the passive dosimeters versus the "know n" concentrations gave a V intercept of --0.004 mg m3 and a slope of 1.003. Tests for the cflccts of face velocities from 25 to 125 cm sec (50 to 250 fpm) did not appear to have any adverse effect on performance, w hilc 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 hydrogen 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 FIX' meter and the L.ASL 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 sy stems 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 vaporsamplingand analytical methods.133' The design of this laboratory experiment involved inter comparison 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 pas.xiv c dosimeter, exhibited good precision over the concen tration range of 0.05 to 0.2 mg m3 as shown in Table 1. 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 v apor.`3<) The sampling media is referred to as "Hydrar Sorbent."and "extensive" but unpublished field and laboratorv 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 `Hopcahte.' " Quantitative determination is made bv chemical desorption of the mercury and analysis with atomic absorption. nitrogen dioxide In 1976. Palmes et al. reported the results of theirevaluation of a personal sampler for nitrogen dioxide (NOs).1351 This work was an extension of their earlier pioneering efforts in developing a personal sampler, employing the principle of gas diffusion, for sulfur dioxide.I2`' In their design, the samplingdevicewasa 1.3 cm (0,5 inches) aery lie tube. 7.1 cm(2.8 inches) long At the "closed"end of thediffuxion path (tube) were placed three stainless steel grids coated w ith triethano lamine (TEA) TEA was selected because. I) it captures NOj efficiently . 2) it provides a stable sampling surface, and 3) it yields a chemical complex with NO.) that is very stable over time. Subsequent analy sis y ielded a colored complex w hose absorption was measured at 540 nanometers. Results were then compared against a standard curve w hich obeyed Beer's Law. The experimental evaluation of the NO; sampler involved chamber measurements compared with "known" values determined by the volume of NO? introduced to the chamber or the weight loss of NO; 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 that 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 analysis. In the prev iously described studies with the G ASBADGE. Tompkins and Goldsmith also monitored for nitrogen diox ide.11' Their summary results for 82 observations showed accuracies and precisions as summarized in Table I. Eightvfive 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).<36' 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 dev ice are show n in Table l.<3,1 'i? Am )nd Hyf Assoc J (43) August 19ET 3H 009936 sulfur dioxide As noted previously, pioneering work in 1973 on the design ol a sampling device which relies solely on diffusion of gaseous contaminants through a stagnant air layer is attrib uted to Palmes and Gunnison/221 Their initial studies in\olved 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 by both wet chemical and conductr imetric measurements. Although this studs did not go into the ramifications of environmental effects and inter ferences. it should be recognised 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 1. 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 I.<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 DosimeterA Bias1' Precisionr Range" (ppm) Reference Notes Carbon Tetrachloride Toluene Formaldehyde Benzene Ethylene Oxide Halothane Enflurane Acrylonitrile Hexane Vinyl Chloride Methyl Chloroform Tnchloroethyiene DPA DPA NMS DP DPB NMS NMS 3M 3M 3M NMS NMS R 3M DPA NMS 3M DPA NMS 04 0.3 -1 7 15 33 -4 1 18 -1.4 3 -2.8 0 03 -1.2 -02 -5.9 -106 24 -3.9 -6 9 -05 44 5.25 1.7 63 47 1.7 17 3.2 7.4 4.8 8.7 2 37 47 45 2 7.6 77 1.9 3 18 57-228 12-47 0 2-4 2 3-24 0.8-5.4 13-13 5 300 0.5-20 0.5-20 07-19 10-37 1 5-14 160-840 160-840 15-65 20-200 20-200 15-67 10 45 13 55 46 13 1 53 44 44 39 13 2 48 48 12 48 48 12 E FJ FJ EG J J J J FJ HJ 1 <1 KU FJ tJ EIJ FJ = 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 BSee text, equation (8) "See text, equation (7) Some values are rounded to nearest whole number ESmall sample sire Knowns were calculated using charcoal tubes with critical orifices. This could affect the bias measure. ``Preliminary results "Permeation dosimeter Bias consistently negative JResults calculated from data provided in reference Ameucan Induslnal Hygiene Association JOURNAL m 8'82 3M 009937 613 activated charcoal devices \s of March. 1982. there were four manufacturers of passive uosimeters which rely on diffusion and subsequent adsorpt.on on to activated charcoal, \ational Mine Service Com pany (GASBADGE). 3M Company (Organic \ apor Momi r). DuPont Company (PRO-IEK. G-AA and G-BB (trgamc Vapor Air Monitoring Badge), and the Mine Safety ppliance Company (Vaporgard Badge) In 1977, Tompkins and Goldsmith described the first i. mmercial passive dosimeter for monitoring organic v .ipors.1" The GASBADGE relied on molecular diffusion of the vapor into the badge and subsequent adsorption onto c. mated charcoal The authors developed the theoretical principles of the badge's operation, and discussed sensitiv itv i temperature and pressure, face velocity effects, and -sponse time Preliminary results showing the badge's response to ben/ene. ethvl acetate, methyl ethyl ketone, and ivrene also were presented and were described as "very l icouragmg" (see "I able II). In the same year. Silverstein reported results of laboratory . ,d field testing of the G ASBADG E for aery Ion it rile Wl The suits ol the exposure of 33 badges to known concentraons in the laboratory are presented in Table II The results dicate the acceptability of the GASBADGE for measureents of acrylonitrile over the range of 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 presented, Silverstein also looked at -sorption ettieieneies and determined that the best results 4 percent) were obtained with four ntL ot two percent etone in carbon disulfide. In 1978, Bamberger et at. conducted a series of laboratory sts to evaluate the GASBADGE.11'1 Their approach inv olved ie generation of known concentrations ol solvents and lbsequent evaluation with charcoal tubes (active sampling) nd the passive dosimeter. To evaluate the applicability of ie dosimeter over a wide range ol compounds, the investimon included seven different organic compounds each . piesentative ol a different tunctional group. Included in his study were ben/ene (aromatic), n-butanol (alcohol), '-butyl acetate (ester), isooetane (alkane), methyl chloro'rml halogenated alkane), methy I isobuty I ketone(ketone), id trichloroethylene (halogenated alkene). The diffusion aefficient ( D) used was that supplied by the badge manufac,rer, except in the case ol isooctane which was reported as aving an unknown coefficient. Computations involving oils compound relied on the coefficient tor n-octane. A v ariety of experiments was conducted to look at a wide range of questions. Their findings corroborated dosimeter con cerns similar to those of active sy stems using charcoal tubes, e g.. minimum and maximum loadings are important, postimple contamination and loss can occur it the exposed bsorbent is not adequately sealed, percent recovery for uxtures is consistent with percent recoveries for single ompounds, and differences in charcoal lots can give differnt results. Other tests confirmed the need for some air movement across the badge lace and the lack ol ellcct ol temperature changes over a small range ( I I ' C ). I he results ot 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 adsorpt ion desorption elttciencies less than 100 percent can be accomplished (Ust as is done for charcoal tube data. In 1979. Hirayama and Ikeda evaluated the application ol the GASBADGE lor monitoring exposures to mixed sol vents.("'1 Their research involved different preparations ol activated carbon "felt" m place ot the supplied collection medium and exposure to mixtures ol n-he\ane. cthv I acetate and toluene. Summary (graphical) data indicated that the amounts of contaminant absorbed by the dosimeter wetc proportional to both the vapor concentrations and time ol exposure. Hallidny and Anderson repotted on the use ol the GASBADGE in monitoring toi halothane 1 Six observa tions indicated a range of measurements Irom munis nine to plus ten percent of the test atmospheres f'ntortunately. the authors did not report their procedure for determining the concentration of halothane in the test atmospheres. In 1981. Evans and Horstman reported evaluations ol desorption efficiencies ot charcoal tubes and the G ASBADG E for styrene.'1'1 For liquid dosing they lound the dosimeter to be similar to the tube, vv hile for vapor dosing the badge was superior. The authors suggested that the dillerences in results may. have been related to the use ot coconut shell carbon in the tubes and petroleum derived carbon m the badge. They did not explain w hy this difference would affect one method of dosing and not the other In 1980. Anders and Mullins of the 3M Company pre sented results comparing the 3 M passive monitor with char coal tubes in sampling for mi xtures of organic compounds 1111 The laboratory tests included a binary mixture of toluene and methyl ethyl ketone: a tertiary mixture of ben/ene. toluene and xylene; and complex mixtures ol unleaded and leaded gasoline containing various alcohols. Although the investigators cited "excellent" precision and accuracy for the ditlusional monitor, sample sizes were small, and the com plicated study design and lack of raw data preclude the determination of precision and bias statistics. Ma/ur and his co-workers'"' conducted side-by-side laboratory and field tests with charcoal tubes and 3M organic vapor monitors to measure concentrations of halo thane (2-bromo-2-chloro-l. I. I-trifluoroethane) and entlurane (2-chloro-l ,1,2-trif\uoroethyl difluoromethvl ether) The results of the laboratory studies are presented in Table II and support the authors' conclusions that the dosimeters are a reliable method for the collection of enflurane and halothane. In 1980. Lautenberger et a!, described DuPont's passivemonitor for organic vapors."" Each charcoal strip in the PRO-TFK G-AA Organic Vapor Badge contains approxi mately 300 mg of coconut-based activ ated charcoal impreg nated in an inert polymer. A dual sampling rate of approxi- t Am Ind Hys Assoc J f-13) August 1982 3M 009938 match 5() or 11)0 nil min is dcirrminal hv ihe rcmouil ol' one or both ol the dosimeter's protect iv e eo\eis. One aspect ot their research in\ ohed experimental determination ol the dilltt'ion coellicient ol several eases and sapors Thee reported that \alues calculated hv I ugg1 *' were within 10 percent ol their experimentally determined diltii'ion coelticlent values, Prelimmaiv experimental results were used to d iscuss lace v eloeits e Meets i a nee a nd sen sit iv its, ma \ imurn and minimum xa mpling times, sapor retent ion, storage stabilits, desorption elticiencs, and oserall badge elliciency. 1 he oserall accuracy deter mmat ions ssere limited to lour iibsers at ions at each ol tsso concentrations ol carbon tetrachloride (see Table II) Howeser. the presentation ol mss data, as well as an explanation ol the statistical tests applied, is most useful, This same detail ol information is also lourid in DuPont's salidation reports lor toluene and hen/ene I see Fa hie II)"1"" I n t he ben/ene report. I >u Pont also describes its PR0-1 E K G-BB badge This badge has a backup section ol charcoal, sshich serscs the same pin pose as the second section in a charcoal tube, i.c . to aid in determining it the sampler has been overloaded. 1 he 3M C ompany also marketsan Organic \ apoi Monitor w ith a backup section.11,1 In studies ol the measurement ol waste anesthetic gases with passixe dosimeters, Jonas ei al. exttluated the GASBADGE. 3M Organic Vapor Monitor and DuPont Pro-1 ek in measuringenllurane. hl Unfortunately, the badges were not identified in the presentation of the results although i nterpretation of t he reported sampler geometry would ind icate that A was the Du Pom badge. B was the 3M badge, and C was the CiASBADGE The results of their laboratory studies indicated that badge B had the lowest coefficients of \ a nation (C V was not calculated as described in this text) as compared to concentrations determined by infrared analy sis Badge A had a loss 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 I I to 27 percent, that desorption efficiencies for the badges ranged from 0 SI to I 17. and that IR analyses of tank concentrations were constantly lower than expected. If badge B was the 3 M dex ice. the results of Jonas et at. support those reported by Mazur e/tf/.1141 Further testing of badges A and C seems necessary. however. to confirm their seeminglv low precisions. Ma/ur and his coworkers conducted additional tests comparing the 3M and DuPont badges against charcoal tubes.'1''1 Methyl chlorolorm and trichloroethy lene, two sol vents widely used in vapor degreasing operations, were sampled. In the laboratory phase of the study, the badges and charcoal tubes wereexposed tochamberconcentrations over the range of 160 to 840 ppm of methyl chloroform and from 20 to 200 ppm of trichloroethylene. Exposure times varied from two to six hours for methyl chloroform and trom tour to six hours for trichloroethy lene. The laboratory work indicated that the percent recoveries ot the various doses (concentration X time) were in good agreement except for one exposure of the 3M badge which involved a five hour Afr*f<tan industrial Hygiene Association JOURNAL m 8 82 exposure at 700 ppm. 1 he author', noted that this exposure ol 3500 ppm-hours exceeded the upper exposure limit pro vided by the manufacturer The overall mean reeoverv value lor each ty pe ot sampler was Used to correct all subsequent held data In addition to the recovery measurements, the laboratory phase ol this study also involved determination ot storage stability. The authors lound no significant losses of methv I chloroform or trichloroethy lent' Irom cither badge following storage of exposed badges tor up to three weeks. In 1978, West and Reis/ner reported on the lield tests of the M I NT MONITORTM ( R E A L. Inc.) permeation personal monitor lor vinyl chloride. "' This monitor was a modified version of one previously described by Nelms el al.'1'1' 1 he collecting medium was activated charcoal, but rather than rely mg on molecular diffusion, the badge design inv olv ed a polymeric membrane and the permeation ot vinyl chloride through the membrane and adsorption onto the ehareoal Initial laboratory calibration was used to determine the permeation constant ot the device, Laboratory results indi cated good accuracies as summarized in fable II During the same period that Tompkins and Goldsmith" were describing the GASBADGF.. Bailey and HolhngdalcSmith of Great Britain were presenting their ideas lor a personal passive sampler lor organic gases and vapors. Their design involved the use of either one ol two tvpes of membrane and subsequent adsorption onto activated char coal. They found two membranes to be satisfactory one ol thin silicone rubber w hich acted as a permeation barrier, and the second a porous polypropylene him which allowed tor molecular diffusion ol the gas and vapor. They conducted laboratory tests using carbon tetrachloride, styrene and dtchlorodilluormethane 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 earlv demonstration of the feasibility of such a dev ice lor monitor ing certain organics The device, the Porton Dittuxion Sampler, seems to see its greatest use in Great Britain acrylonitrile One ol the newest applications of passiv e dosimetry inv olv es the use of a porous poly mer ( 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 1,1> 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 aery Ion it rile 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 Konzen constructed passive dosim eters from glass culture tubes (1.05 cm inside diameter) with 40 60 mesh silica gel as the collecting surface.1''"1 Laboratory testing involved exposure of the dosimeter to aniline, with exposure concentrations determined bv gas chromato graphic analysis of ethanol gas scrubbers Three different 3M 009939 BIS si7e (length) dosimeters were evaluated. w ith the best results obtained with 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 hare recently described the 3M diffusional monitor for sampling ethylene oxide in air.`,V11 In this badge the collecting surface is described as a "chemically impregnated charcoal surface, (where) a reaction occurs producing a stable compound with a sapor pressure sub stantially lower than the parent compound." The authors present statistically summari?ed data describing the linearity and capacity of the monitor, the recov ery of absorbed ethyl ene oxide, cm ironmental effects, sample stability, and the effects of potential interferences. Precision and bias are presented in Table 11 formaldehyde Rodrigue? ci al. ha\c described another 3M diffusional monitor for sampling formaldehyde <M| In this diffusional monitor, the collecting surface is an "impregnated sorbent" which can then be desorbed in .sun with water and the concentration of formaldehydedetcrmined colorimetrically. Laboratory evaluation first in\ olved determination of recovcry coefficients, which at eight ppm-hours (19.5 micrograms) were found to be 1.00 0.04 oxer 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 relatixc humidity on the sampling rate also was mxcsfigated. 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 inx olved simultaneous exposures of inrpingers (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, howev er 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 chromotropic acid-sulfuric acid reaction Laboratory evaluation (42 samples) of the dev ice at seven exposure levels revealed results as shown in Table II.15'" Additional studies also were conducted on tempera ture and storageeflects. The raw data and statistical analysis procedures arc presented Kriesel'1'61 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 device are not available phosgene Matherne et al. have recently described the GMD. Inc "passive dosimeter"which prov ides a semiquantitative mea surement ol phosgene exposure 15,1 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 be logarithmically proportional to the phosgene doseovera range of2to 100 ppm-minutes. For quantitative measurements the badges can be read colorimetrically, other methods Hill and Fraser have described the use of commercial detec tor tubes modified to act as passive dosimeters In then research, common length-of-stain detector tubes were modi fied by cutting off the conical end of the tube and remov mg some of the indicator column material This leaves an on I ice w ith a cross-sectional area equal to that of the inside ot r he tube and a path length determined by the distance from the end of the tube, to the beginning of the indicator matetia! One would expect, however, that as the sorbent mateiul 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 isopropanol. 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 dioxide1' 1 and chlorine.'" have been identified For organic compounds, eight stud ies'3,939,44 4i>M have involved 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 sire or insufficient presentation of data. Jones ei al.lb` conducted a field evaluation for NCL 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 giv es a correlation coefficient of 0.69. a slope ol 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 foi 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 Bit Am Ind Hy Assoc J(43 3H Q09940 values to be low as compared lo 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. Hardv ei al.'2hi reported the raw data results from a field evaluation of a permeation chlorine monitor (RFAL. Inc.). Thirteen comparisons were made in w hich the results from a battery operated pump and an impinger sampler were compared 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 l.l ppm as detected by the impinger It should be noted that with five impinger samples ot less than 0.1 ppm. the corresponding permeation dev ices detected considerably higher concentrations (0.16 to 0,4 ppm I Silverstein1'191 reported field results for acrylonitrile moni toring using 18 paired samples of CiASBADGE passive monitors and active systems (charcoal tubes and pumps) over a tangc of 0.8 to 5.8 ppm as determined by the active method I he differences in results using the active system as a reference ranged from --0 7 to 1.5 ppm. f he difference in means. 2 18 for t he passiv c v ersus 2.75 I or the activ e system, was 25 percent Further data were not presented. West and Reis/nei reported five sets of field results for viny I chloride sampled w ith permeation dosimeters (RE AL. Inc ) and charcoal tubes Further interpretation of their results is presented in Table III. In each case data for the active system are the X values Fout 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 1.51). indicating that badge values may fall either well below or above charcoal tube values. In those cases where the slopes were less than 1.0. very high humidi ties (67 to 91 percent) were reported by the authors. This factor mav 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 5M Organic Vapor Monitors to complex mixtures of organic chemicals in tire manufacturing opera tions.'9' Generally the sampling period ranged from three to TABLE III Regression Analysis of Vinyl Chloride Field Dote'2' N Range (ppm) r Slope Y-Intercept 7 002-1 0 99 1 19 8 0.08-1.8 0 99 0 69 12 0 02-6.9 1.0 1.31 39 0 05-1.8 082 0 81 24 1 48-16.7 0,96 1.08 0 03 0 05 0.01 0.11 0 43 American Industrial Hygipnp Association JOURNAL (43'8 `82 five hours, and most observations consisted of one monitor and the time weighted average concentration front two sequentially exposed charcoal tubes Sixty-four of the sets were personal samples, while the remaining 14 were area 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 wide range of concentrations to allow lot appropriate statistical analysis by linear regression The results are interesting in that in the first plant, 9 of the 10 organtes 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 5-intercepts (Y^passive dosimetet data) were slightly negativ e. 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 lev el. 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.<19'Thiscondition can onlv be revealed through regression analyses. In 1980, Mazur et al.,4il reported limited field data lor halothane and enflurane measurements using both 5M 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 system) of five percent. Only one data pair was reported for enflurane- 0,49 ppm for the OVM and 0.52 ppm for the active svstem Obviously, more data are needed to draw conclusions regarding a comparison of the two methods for these agents. A second study by Mazur er o/.HSl reported field compar isons of passive dosimeters and active systems (pumps and charcoal tubes) in sampling for trichloroethy lenc(TCE) and methylchloroform(MC). Both DuPont PRO-TEK and 3M Organic Vapor Monitors were used for the passive sv stems. Personal samples included exposure of one each of all three monitors. Area sample results involved three average values: one was the average of three charcoal tubes, and the other two, the average of two of each type of dosimeter. For MC. 11 personal and 7 area data points collected over time peri ods of I to 5 hours at 15 to 21 Cand 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 which 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 009941 617 CO. TECH. BROCHURE,(REPRINT OF PAPER PRESENTED AT A1 HA ME , 1978 HARDY, J.K., D.T. STRECKER, C.P. SAVARIAR AND P.W. WEST , " A METHOD FOR THE PERSONAL MONITORING OF HYDROGEN SULFIDE USING PERMEATION SAMPLING ", AM. IKD. HYC. ASSOC. J 42< 2 ) : 283 - 286 , 1 ?8 I HARDY, J.K., P.K. DASGUPTA, K.D. REISZNER AND P.W. WEST , PERSONAL CHLORINE MONITOR UTILIZING FERMEATION SAMPLING ", SCI. TECH. 13:1090-1093 , 1979 "A ENVIRON HARRISON, J.W., LAWLESS, P.A., RESEARCH TRIANGLE INSTITUTE , DOSIMETRY ", EPA < ESRL/ REPORT 1976 GILEERT, D.E., AND WHITE, J.H , " DEVELOPMENT STRATEGY FOR POLLUTANT EPA-600 / 2 - 76 - 034, NT I S PB-265-910 , HEARL, F J. AND MANNING, M.F. , " TRANSIENT RESPONSE OF DIFFUSION DOSIMETERS ", AM. IND. HYG. ASSOC. J. 41, 778 , 1980 HILL, R.H AND D.A. FRASER , " PASSIVE DOSIMETRY USING DETECTOR TUBES ", AM. IND. HYG. ASSOC. J. 4 1 ( 1 0 ) : 7 2 1 - 7 2 9 , 1 980 JONES, L.C., BILLINGS, C.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 D.A. REAVELEY , " AN EVALUATION OF THE PORTON DIFFUSION SAMPLER FDR LONG-TERM MONITORING OF HALOTHANE 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 , 1 9,80 MORELLO , IND. HYG. " A NEW PERSONAL ASSOC. J. LUGG, G.A. , " DIFFUSION COEFFICIENTS OF SOME ORGANIC AND OTHER VAPOR IN AIR ", ANAL. CHEM. 40 1072 , *768 MATHERNE, R.N., P.L. LUES AND E.S. KERFQOT , " THE DEVELOPMENT OF A PA5SIVE DOSIMETER FOR IMMEDIATE ASSESSMENT OF PHOSGENE EXPOSURES ", AM. IND. HYG. ASSOC. J. 42:6ei-6e4 , 1981 MAZUR, J.F., D.S. RINEHART, G.G. ESPOSITO, AND G.E. PODOLAK , EVALUATION OF PASSIVE MONITORS FOR ASSESSING VAPOR DEGREASER EMISSIONS ", AI HA JOURNAL 42, 752-756 , 1 98 1 3M 009947 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, 66-69 , 1 980 MAZUR, J.F., G.E. PODOLAK, G.G. ESPOSITO, D.S. RINEHART, AND R.E. GLENN , " EVALUATION OF A PASSIVE DOSIMETER FOR COLLECTION OF 2-BROMO- 2-CHLORO-l,1,1,-TRIFLUOROETHANE AND 2-CHLORO-1,2,-TRIFLUOROETHYL DIFLUOROMETHYL ETHER IN HOSPITAL OPERATING ROOMS ", AI HA JOURNAL, 41, 317-321 , 1980 page 3 MAZUR, Jr., R.L. EAMEERGER, G E . PODOLAK, AND G G. ESPOSITO , DEVELOPMENT AND EVALUATION OF AN AMMONIA DOSIMETER ", AI HA JOURNAL, 39, 749-753 , 1978 MC GAMMON, C.S. AND J W. WOODFIN , " AN EVALUATION OF A PASSIVE MONITOR FOR MERCURY VAPOR ", AM IND. HYG ASSOC. J. 38.378-386 19 77 , MC DERMOTT, D.L., K.D REISZNER AND P.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, H.E. AND L.W. ANDERS , " A NEW INNOVATIVE DIFFU5I0NAL MONITOR FOR SAMPLING ETHYLENE OXIDE IN AIR ", AM. IND. HYG. ASSOC. <IN PRESS) , J. NADEAU, J.S. AND D.G.E. BOOCOCK , " STABLE FREE RADICAL REAGENT AND SOLID PHASE SUITABLE FOR A NITRIC OXIDE DOSIMETER ", ANAL. CHE. 49 : 1 672- 1 676 , 1 977 NADEAU, J.S., M.E. TREEN AND O-C.B. BOOCOCK , " MASS TRANSFER EFFECTS IN A NITRIC OXIDE DOSIMETER. ", ANAL CHEM. 50:1871-1873 , 1978 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 OROFINO, T.A. AND A.M. USMANI , JULY:96-104 , 1980 " PASSIVE DOSIMETRY ", AM. LAB PALMES, E.D. A F. GUNNI5IN, J. DI MATTIO AND C. TOMCZYK , " PERSONAL SAMPLER FOR NITROGEN DIOXIDE ", AM. IND. HYG. ASSOC. J. 37:570-577 , 1976 PALMES, E.D. AND R.H LINDENBOOM , " OHM'S LAW, FICK'S LAW AND DIFFUSION SAMPLERS FOR GASES. ", ANAL. CHEM. 51:2400-2401 , 1979 PALMES, E.D., A.F. GUNNISON, J.D. MATTIO AND C. TOMZYK , " PERSONAL SAMPLER FOR NITROGEN DIOXIDE ", AM. IND. HYG. ASSOC. J. 37:570-577 , 1976 PODOLAK, G.E., R.M. MCKENSIE, D.S, RINEHART, AND J.F. MAZUR , " A RAPID TECHNIQUE FOR COLLECTION AND ANALYSIS OF PHENOL VAPORS ", AI HA JOURNAL, 42, 734-738 , 1981 PROCEDDINGS OF AN ACGIH TOPICAL SYMPOSIUM, CINCINNATI, OHIO , DOSIMETRY FOR CHEMICAL AND PHYSICAL AGENTS ", 1 , 1980 PURNELL, C.J., WRIGHT, M.D., AND BROWN, R.H. , " PERFORMANCE OF THE PORTON DOWN CHARCOAL CLOTH DIFFUSIVE SAMFLER ", ANALYST 106, 590 , 19 8 1 REISZNER, K.D. AND P.W. WEST , " COLLECTION AND DETERMINATION OF SULFUR DIOXIDE INCORPORATING PERMEATON AND WEST-GAEKE PROCEDURE ", ENVIRON. SCI. TECH. 7:526-531 , 1973 RODRIGUEZ, S.T., P.B. OLSON AND V.R. LUND , COL ORMETR1C ANALYSIS OF 3M 009948 page 4 FORMALDEGYDE COLLECTED ON A DIFFUSiONAL MGNITOR ", AM. IND HYG. ASSOC. J (IN PRESS) , SCHNAKEMBERC, G. , JR , "US. BUREAU OF MINES TECHNICAL PROGRESS REPORT V 5 ", 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 ", U.S 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, n V., E.L. MASTRACCI AND J.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 , 5ILVERSTEIN, L.G. , " VALIDATION OF ABCOR "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., JR. AND R.L. GOLDSMITH , " A NEW PERSONAL DOSIMETER FOR THE MONITORING OF INDUSTRIAL POLLUTANTS. ", AM. IND. HYG. ASSOC. J . 38:37 1 - 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. J. 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 009949