Document vBnkn9N6v2EMBjqdRyok9YKeE

ISO I00TK Mil* STHEET tiattro m (irutinirti mint Th* B.P. Goodrich Company Ado*. OHIO 4 4 3 1 1 IHOIE: 21I-17I-E11I ADOftESI AEHY TO: OEAT. 0001 110 6. WHI-4 July 12, 1974 Hr. Julius Jimeno Docket 36 1726 M Street, N.W., Room 200 Washington, D. C. 20210 Dear Hr. Jimeno: I am enclosing our laboratory report which fulfills the request by the Office of the Solicitor for further information on the technical details of testing commercially available charcoal filled canister and cartridge protective breathing devices. The experimental approach Is described in detail. The wide range in capacity for absorbing vinyl chloride by commercial absorbants is shown in Table I on page 4 and the clear superiority of activated charcoal is evident. The comparison of cartridge and .canister data in Tables 2 and 3 indicates that depth of carbon bed Is also a factor in capacity which must be balanced against pressure drop in the design of a respirator for breathing protection. The desorption experiments show that the recharging of cartridges and canisters is feasible. Laboratory work is continuing. If further pertinent information develops, it will be submitted before August 23, 1974. Very truly yours, THE B.F.GOODRICH COMPANY k Enc. Director of Environmental Affairs j i .1 1 ` 3517001 BFG25796 r ' V T- i .--:aJ *-:7 T - : ' . ? >* h*i,v :- r-hv^-V-*?^ . 4-L&-. *.. ?.. W. Strassburg AIrrca; Loc. VOKB-4; Dept. OOui f*t< o fywt oa *. ("rMdir iixc. no, C > L\ * I-i.'i:. M. O'Mara Avon Lake Technical CenreJ >M 2i 1974 A-i Investigation of the Adsorption Properties cf Vinyl Chloride Hontmer n Commercial Carbon Filters Introduction This report is a sutmary of our work on the adcci-ptici. chart'etc?!rules of VCH on carbon filters which are used in conjunction with protective breath ing masks. The basic objective of the study was to determine the ndaoz.vlivr and desorptlve characteristics of various, commercially available, l.>\ filters which are used as protection against inhaled organic veporf. T'lic study involved vinyl chloride monomer only. Experimental Approach An experimental flow chamber was constructed so that carbon cartridges and canisters could be subjected to a continuous fiev- cf oil containing vinyl chloride monomer. A continuous rather than batch monitoring method of analysis was chosen to indicate the presence cf vinyl chloride monomer. A photograph of the basic flow chamber is shov.n in Figurv. 1. '.-he vinyl chloride-air stream enters the carbon device at A. The scrubbed --c then exits the device at B. Line C is the continuous monitoring oyrte:. lor sensing vinyl chloride monomer in the eir stream. Additional expatv.v.ir.ta/. data are contained in the Appendix. To demonstrate the type of data that is obtained from the experiment described above, n plot of VCM cou'wr.. -ioa versus time is shown in Figure 2. The risa in the horizontal bateJlie indicates incipient vinyl chloride monomer breakthrough. In our initial experimental design, we used a portable Century organic Vapor Analyzer to sense vinyl chloride monomer. The major problem with this analyzer was its inherent background which could not be subtracted electron ically from the recorder output. To overcome this we replaced this instru ment with a Bciidix Hydrocarbon Analyzer, both instrunencs are. flaca i.eriz* ction units; Figure 2 is based on the output of the Ben-iix instnrenr.. Vc. Bendix instrument is wall suited for the t'ype of mr'-s- .Croat carried ctr. because of the following unique v.hararter::.Rtics: (1) low drift (2) linear (vs. logarithmic) anp:.-..'::: :r (3) background zero suppression (4) excellent stability BFG25797 S.. V. Strascburg Page Two July 2, IS 74 figure 1; Experimental VCH Flow Chamber i i ' ' (A) vinyl chlorlde/air stream into cartridge holder CB) cleaned air stream exit (C) analyzer sampling line (D) vinyl chloride flowmeter (E) high capacity air flowmeter ]; j j \ I 1 BFG25798 3517003 66LSZDd%. 23517004 E. W. Strassburg Page Pour July 2, 1974 Experimental Results (i) Initial Evaluation of Commercial Cartridges A variety of commercial cartridges vere evaluated with the Century inalyzer in order to obtain a profile of their ability to retain vinyl 'thlorlde monomer. All evaluations vere carried out at a flow of 30 liters t>er minute and a vinyl chloride concentration (volume/volume) of 100 partsper-nillion. In these early evaluations, the time to 5 parts per mil.l ion of vinyl chloride at the exit side of the carbon matrix vas determined. This value is referred to as Tj (in minutes). Table 1 contains a 8urinary of the various cartridges evaluated and the corresponding values obtained. Table 1 (1) Values for Various Carbon Cartridges When Tested at 30 liters/minutes and 100 ppm of Vinyl Chloride Monomer Cartridge a) minutes - Welsh 7500-1 41, 34, 39, 44, 33 American Optical A0R55 21 Westvaco Nuchar WV-H 8X30 15 Willson U-25 . 34 Willson R-ll 0 American Optical R-51 29 Willson R-21 Welsh 7400-1L 84- 42 13 93 Welsh (Canister! 7800-1H . . MSA Cartridge 44135 678 13' U)T^ -refers to the time in' minutes for the concentration of VCH at the exit end of the cartridge to reach 5 ppm. BFG25800 R. W. Strassburg Page Five July 2, 1974 It can be seen from these data that the commercial cartridges and canisters chosen for this study exhibit a broad range in ability to absorb vinyl chloride monomer. All of the 3-inch cartridges vere effective from aero minutes (no VCM adsorption) to about 40 minutes. After initial vinyl chloride breakthrough there is a gradual rise to a value corresponding tc the concentration of vinyl chloride in the air scream. As expected, the 4-inch cartridge (Welsh 7400-1L) and the canister outperformed the 3-inch cartridges under these test conditions. It should be noted that in the end-use raask construction, two of the 3-inch cartridges are used. On the other hand, a single ^-inch cartridge or canister is use in masks employing these carbon devices. Thus to obtain a true evaluation of the 4-inch cartridge and canister, they must be exposed to an air flcv that is double that used for the 3-inch cartridge evaluation. This type of evaluation is described below. (ii) Detailed Evaluations of the Welsh Canister, 3-inch Cartridge and 4-inch Cartridge The NIOSH requirement for testing protective masks calls for evaluations at the following atmospheric flow rates: 32 liters/minute and 64 liters/ minute. The Welsh canister (780CblM), the Welsh 4-inch cartridge (7400-.'L) and the Welsh 3-inch cartridge (7/iOO-l) were evaluated within these guide lines. Testing with the 3-inch clrtridge was restricted to a flow rate of 32 liters/minute while that for the 4-inch cartridge anJ canister wa3 limited to a flow rate of 64 liters/ninute. In order to improve the accuracy of the measurement, a Bendix Total Hydrocarbon Analyzer was obtained for monitoring vinyl chloride monomer. Using this instrument in the experiment approach described above, measurements at 1 ppm VCM breakthrough (T^) could bn accurately obtained. Tabic 2 contains a summary of Tj_ values obtained for the three Welsh cartridges and canisters. These data show that vinyl chloride breakthrough (T^) is essentially the same for the 3-inch and 4-inch cartridges when tested at the two required flow rates. It is also obvious that breakthrough is quite dependent upon concentration. For the two cartridges, a 4-fold increase in VCM concentration caused a 502. increase in breakthrough time. The stronger depender-e of 7CM/air rate on breakthrough time is demonstrated by comparing data . a Table 1 with that in Table 2. For example, comparing Tj data (accurate T^ data is not available in Table 1) it is seen that for the 4-inch cartridge there is a 50Z increase in breakthrough (Tc) when the rate is increased from 30 liters/ minute (Tj = 93 minutes) to 64 liters/minute (T^ = 48 minutes) at a VCh concentration of 100 ppm. BFG25801 qnnATSS?. R. V. Strassburg Page Six July 1974 i TaSle 2 Values for the Welsh 3-inch, 4-inch Cartridges and Canister at Various Concentrations of Vinyl Chloride Monomer 1. Welsh 7500-1 (3-inch) / 32 liters/minute VCH, ppm 25 50 100 71. Welsh 7400-1L (4-inch) 64 liters/-ninute VCM, ppm 25 50 100 Xj, minutes 60 60 l 35 (Tc *= 44 minutes) Tl, minutes 70 60 40 (Tij 48 minutes) III. Welsh 7800-1M (Canister) 64 liters/minute VCM, ppm 25 100 1000 T^, minutes 522 (8.7 hrs.) 342 (5.7 hrs.) 102 (1.7 hrs.) <D refers to the time in minutes for VCM concentration to reach BFG25802 /  - .7 r -->- R. V. Strasbourg Page Seven July 2, 1974 I* t Considering only those data in Table 2 it can be shown that the ount of vinyl chloride adsorbed increases with increasing concentration of . .. _yl chloride in the air stream. The absolute amount of vinyl chloride ad; ::d by the carbon in each of the experiments can be obtained from the foli :hg equation: VCM, cc *= total rate (cc/min.) X concentration VCH To 1 i 1 { 5 5 where T0 is initial breakthrough at "zero" parts per million. Once obtained^ relative VCM adsorption efficiences can be calculated by dividing these values by the weight of the carbon in the cartridge. /. summary of these data are contained in Table 3. It is evident that fbe efficiency of carbon to absorb vinyl chloride monomer is not constant but rather increases as the concentration of vinyl chloride monomer increases in the air. It is significant to note that the efficiency of carbon to adsorb vinyl chloride monomer is nearly constant for the two cartridges when compared at the same vinyl chloride concentration, even though the flow rates are significantly different. This sameness in efficiency, of course, relates back to the previous statement that these two cartridges offer the same degree of protection. As a final comment the very high efficiency of the carbon bed in the canister is responsible for the excellent (relative) protection this device provides. It appears that empetical mathematical equations describing break through times for the two types of cartridges could be readily developed ! since the adsorption efficiency at a given VCM concentration is constant. Ecwever, before this Is attempted more data would be necessary at different flew rates and over a broader concentration range. ma a a BFG25803 R. W. Strassburg Page Eight July 2, 1974 Table 3 Calculation of Absolute Adsorption of VCH (cc) on Carbon and Efficiencies (cc VCH/g Carbon) I. Welsh 7500-1 (3-inch) 32 liters/minute VCM, ppm 25 50 100 VCM Adsorbed, cc 48.0 82.4 108.8 Efficiency^. -gc/s 1.34 2.29 3.03 II. Welsh 7400-1L (4-inch) 64 liters/minute VCM, ppm 25 50 100 VCM Adsorbed, cc 88.0 160.0 227.0 Efficiencv^^. cc/e 1.31 ' 2.38 3.39 III. Welsh 7800-1M (Canister) 64 liters/minute VCM, ppm VCM Adsorbed, cc 25 100 1000 777.6 1958.4 6336 (1) cartridge contained 35.9g carbon (2) cartridge contained 67.Og carbon (3) canister contained 310.3g carbon Efficiencv^^. -C?/.P 2.51 6.31 20.4 6 (H ) T S R. W. Strassburg Page Nine July 2, 1974 *l (iii) Desorptioa of Vinyl Chloride Monomer It was of interest to study the desorption characteristics of vinyl chloride monomer from the cartridges. To accomplish this objective, the 3-inch Welsh cartridge was exposed to vinyl chloride monomer at 100 ppm and 32 liters/minute until initial breakthrough at 1 ppm (i.e. Tj) was achieved. At this point the vinyl chloride feed stream was 6hut off ana the cartridge was exposed to clean air at 32 liters/minute. A skewed bell-shaped curve developed which maximized at 33 ppm (time = 84 minutes) and decreased to 0 ppm (time = 330 minutes). In actuality we were producing a gas chromatogram in t&ich the carbon canister was a crude chromatographic column, the air was the carrier gas, the vinyl chloride was the sample and the Bendix analyzer was the detector. It is well known that one way to decrease the retention time in gas chromatography is to increase the flow rate. To demonstrate this phenomenon with the present system, we repeated the above experiment (3-inch cartridge, 100 ppm VCM, 32 liters/minute) except once initial VCM breakthrough occurred the vinyl chloride feed was discontinued and the clean air rate was increased to 64 liters/minute. At this increased flow rate, the bell shaped "chromatographic" curve was less skewed. The maximum now occurred at 36 ppm (time = 49 minutes) and decreased to 0 ppm (time = 194 minutes). This trace is shown in Figure 3. Thus by doubling the "carrier gas" flow rate from 32 liters/minute to 64 liters/minute, the "retention time" decreased by 42%. It is obvious that ocher chromatographic principles can be used to further decrease the desorption time of VCM on carbon. For example, higher flows in combination with heat could potentially lead to very rapid removal of the VCM from the carbon. (iv) Performance of Cartridge after Repeated Adsorption-Desorption of Vinyl Chloride Based on chromatographic principles, the cartridges used to adsorb vinyl chloride should be reusable once desorption has been carried out. To verify this, a 3-inch cartridge was exposed to vinyl chloride and desorbed at 64 liters/minute. This was repeated twice. This "regenerated" cartridge was then exposed to VCM at 100 ppm and 32 liters/minute. It was found that the efficiency to absorb vinyl chloride monomer was the same as found for a new cartridge. The breakthrough times for the regenerated cartridge were Tj_ = 35 -minutes and = 45 minutes. These values are identical to those values reported in Tat/le 2 for a new 3-inch cartridge. BFG25805 0TJ>4T oo CA T T O Z .T S P BFG25806 / Appendix I 1 1 \ \ : i ZTQ LX seZ BFG25807 Experimental ' . - , *' V' Vlnvl Chloride Standards : "J'" Vinyl chloride monomer In air standards (19, 900, 9990 ppm) were obtained commercially from Precision Gas Products, Inc., Kahvay, New Jersey 07065. Cartridge 8-Canisters ' All cartridges and canisters were obtained commercially from the suppliers already mentioned. All devices were tested as received. Make-Up Air In order to attain the high flow rates necessary, in-plant compressed air was used to dilute the vinyl chloride standards. This air stream was purified by means of an oil filter and a 9-inch (length) by 5-incb (diameter) carbon bed. ./,#* /i uriiiu, fy <t~ /v* Lc ty, 'the. Cur hurt UunuJi`hj erf Flowmeters . . CUCi, /Ls~/j V. b.c7r + * cff- *7'/ *`rT C' i-fie-tf /ocn-r--IIbI)y ltz<( All streams were metered with F. & P. Co. precision bore flowmeters. Vinyl Chloride Analyzers/Recorder The Century Organic Vapor Analyzer used in the initial phases of this work was purchased from Century Systems Corp., Arkansas City, Kansas 67005. The Bendix Total Hydrocarbon Analyzer (Model 8401) was purchased from Bendix, Ronceverte, W. Va. 24970. A Hewlett-Packard Model 7101B Strip Chart recorder was used to display the outputs from the Century and Bendix instruments. BFG25808