Filtering facepieces: Study supports need for fit-testing Reuse of organic vapor chemical cartridges By Craig E. Colton, C.I.H. Craig Colton is a Certified Industrial Hygienist with the 3M OH&ESD Laboratory. 3M™ Service Life Software Version 2.0 offers new features Do I need a respiratory protection if...? Voluntary use and related issues 3M OH&ESD announces training courses for 2000

In a recent report on the performance of N95 filtering facepiece respirators, published in the Morbidity and Mortality Weekly Report, researchers from the National Institute for Occupational Safety and Health (NIOSH) concluded that conducting a fit-test prior to respirator assignment increases respirator performance.(1) This means using a fit-test to select a respirator that fits appropriately can increase the protection a respirator provides. This article describes the NIOSH study and discusses the results. Laboratory vs. workplace studies NIOSH used a laboratory performance study (rather than a workplace performance study) to evaluate the effects of fit-testing on respirator performance. Researchers determined the total penetration of a laboratory room aerosol into respirators with N95 filters while they were being worn. A Portacount Plus™ fit-test apparatus was used to measure particle penetration. The equipment utilizes ambient particles (room air particles) as the challenge agent. However, the Portacount only measures fit when a 100 level filter is used, because the 100 level filter eliminates filter penetration so only faceseal leakage is measured. The particle size distribution of ambient particles in room air contains many particles in the most penetrating size range for respirator filters. Since an N95 particulate filter is not 100% efficient in removing these particles, the reported penetrations include both filter penetration and faceseal leakage. In addition, particle size distribution in a workplace is very different than that of a laboratory room. Workplace particles are typically much larger. Consequently, it is difficult to extrapolate the particular performance of these respirators to the workplace. However, while these data may not indicate performance in the workplace, the study allows one laboratory measurement to be compared to another. The NIOSH experiment had two parts. Part 1 measured laboratory performance without fit-testing. Part 2 measured laboratory performance only on those people who passed a fit-test. NIOSH study part 1 In this phase of the study, a test panel of 25 people wore 21 different models of N95 filtering facepiece respirators. No fit-testing was conducted to select appropriate-fitting respirators. Every person wore each model of respirator regardless of fit. When a given model of respirator was available in multiple sizes, the size with the best subjective fit was used. User seal checks were performed according to the manufacturers' instructions. Previous work has shown that user seal checks cannot be used as a substitute for fit-tests.(2) Both the Occupational Safety and Health Administration (OSHA) and American National Standards Institute (ANSI) standards require fit-testing prior to respirator use in the workplace. This is another reason the results of this test phase are not representative of workplace performance.(3,4) After each respirator was donned and a user seal check performed, the total penetration into the respirator was measured while the wearer performed a test consisting of six exercises. The respirator was then removed. Three more identical tests with the same model of respirator were performed on each person. This provided four "performance" measurements on each of the 25 people, yielding a total of 100 measurements for each of the 21 respirator models. These performance measurements (% penetration) can be converted to a simulated workplace protection factor (SWPF). The SWPF is the inverse of penetration: SWPF = 100% % Penetration The fifth percentile is the point in the data at which 95% of the data lie above that point and 5% of the data fall below. Here, the overall fifth percentile SWPF for all 21 respirator models was 3. This corresponds to an overall penetration value of 33%. Therefore, 95% of wearers of these respirators can expect respirator performance greater than this value. These respirator performance measurements indicate performance without fit-testing. The fifth percentile workplace protection factor has typically been used to set the assigned protection factors (APFs) for respirators.(5) Filtering facepiece respirators have typically had an APF of 10.(4) NIOSH study part 2 The second part of the study evaluated the same "performance" measurements after fit-testing had been done. Each respirator model was assessed by removing the results from those people among the 25-person panel who failed a surrogate fit-test with any of the respirator models. NIOSH referred to the procedure as a surrogate fit-test because the "fit-test" method used is: • not commercially available; • not one of the protocols in the OSHA respiratory protection standard, 1910.134; and • was never correlated to any accepted fit-test method. In fact, this sample chamber procedure never passed the experimental stage of product development and the manufacturer has since abandoned this approach as a method of fit-testing respirators with N95 filters. A fit-test is a procedure for evaluating respirator faceseal leakage and determining whether the respirator fits appropriately. Since the fit test method used in this study allowed both faceseal leakage and filter penetration, corrections were made for faceseal leakage. A specially-designed sample chamber was used to measure the amount of filter penetration. To make this correction, the sample chamber was clamped onto the filter and the filter penetration was measured using the Portacount. The Portacount pulled air through the filter into the chamber. It also counted particles that penetrated the filter. In theory, the chamber was sized so the airflow through the filter during the test was equivalent to the airflow through the entire filter that would occur if a person were breathing at a normal work rate. The researchers then calculated a "fit factor." This can be accomplished by using the following two equations: Total Penetration - Filter Penetration = Faceseal Penetration   Fit Factor = 100% % Faceseal Penetration The 25 people were classified into passing or failing fits for each model of respirator by determining if the initial test for each person had a calculated "fit factor" greater than 100. A fit factor of 100 is the standard value used by OSHA and ANSI to assess faceseal leakage of half-facepiece respirators.(3,4) Then the total penetrations measured for trials 2,3 and 4 were used to calculate the fifth percentile simulated workplace protection factor for each person/respirator combination passing the fit criterion. When only the results from those people who passed the fit-tests were counted, the average fifth percentile SWPF increased to 25. This corresponds to an overall penetration of 4%. These results indicate respirator performance only on people passing a fit-test. As a result of fit-testing, the fifth percentile SWPF increased from 3 to 25 while the overall penetration decreased from 33% to 4%. It is important to note that the fifth percentile is greater than the APF of 10 given to this respirator type. NIOSH concluded that performing a fit-test has value in identifying those wearers having poor fit. Discussion This study did not measure actual workplace performance of N95 filtering facepiece respirators. Therefore, it is difficult to correlate the results of the study directly to the workplace for several reasons. These include the test aerosol, the fit-test method, the test panel and the method of selecting the respirator. Test aerosol Particle size distributions found in the workplace are typically larger than those found in a room of a laboratory or office. Therefore, filter penetration in the workplace would be lower than that measured in this study. This would result in a lower value for total penetration and a higher protection factor measurement. Fit-test method Calculating a "fit factor" by subtracting filter penetration is unproven. There are no data to indicate how the fit factor of 100 determined by this method compares with a fit factor of 100 determined by other methods of quantitative fit-testing, or how this compares to passing an accepted qualitative fit-test. This is not an OSHA-accepted method of fit-testing. In addition, the accuracy of the device depends on several assumptions. First, filter penetration is sensitive to airflow velocity. In turn, airflow velocity through the respirator is dependent on the filter surface area, which can be different for each respirator model. The airflow velocity during the test is dependent upon the pump in the Portacount and the size of the sample chamber. Therefore, each person must breathe at a single rate and the rate cannot vary within or among tests or among people. In addition, penetration through the filter must be uniform across the entire surface. Both of these assumptions have been proven incorrect. In our laboratory, we found the device used to measure filter penetration was too variable to be useful in fit-testing. Measuring filter penetration with too low of a velocity compared to the actual velocity when the respirator is worn results in allowing fits that would not be acceptable using OSHA-accepted methods of fit-testing. This would result in lower overall respirator performance being reported. Test panel The test panel consisted of 15 women and 10 men. NIOSH states that the distribution of face lengths and face widths approximated the general population. However, the general population may not represent the workplace population. Some workplaces have a greater proportion of male or female workers, or may have a higher proportion of one ethnic group than another. In addition, the 25-person test panel typically used in studies of this type is based on face measurements of United States Air Force personnel in the 1960s. Today, the makeup of the U.S. workplace population is nothing like that of the Air Force population of the 1960s. Many more ethnic groups and females are found in the current U.S. work force. Size of air force personnel compared to that of the workplace population is another variable. This is why fit-testing on a multi-person panel does not predict fit for a specific individual and why fit-testing is necessary in the workplace. Respirator selection Another factor that makes correlation difficult was the testing of each person with each respirator. In a respiratory protection program, it is recommended that if several respirators are available, a person be allowed to choose the most comfortable respirator, then undergo a fit test. Some respirators are obviously too small or large to fit. Testing each person with each respirator means that marginally-fitting devices were included in the tabulation. The researchers noted that several respirators did not "fit" very many people. This is not surprising because it is expected some respirators are designed for faces of specific size. Many manufacturers make models of filtering facepiece respirators to fit different face sizes instead of making one model of filtering facepiece respirator in three sizes. For example, the 3M 8110S respirator is our smaller-sized version of the 3M 8210 respirator. Instead of making the 8210 respirator in two sizes, we make two different models. We expect the 8110S respirator to fit a smaller percentage of the population, but we expect it to fit smaller faces very well. In other words, if the best fit is obtained with the 8210 respirator, one would not choose to wear the 8110S respirator.   Supporting data Another way to measure respirator performance is through workplace protection factor (WPF) studies. These studies directly measure performance in the workplace by collecting samples inside and outside a respirator while it is worn during work. A number of good workplace protection factor studies have been reported around the world. In the U.S., fit-testing is required, although in Europe it is not. Therefore, some of these studies mandated a fit-test prior to measuring the WPF,(6-18) while others did not.(19-22) Figure 1 shows the distribution of data from these studies on half-facepiece respirators grouped according to whether fit-testing was performed. When fit-testing was used to screen out poor-fitting half-facepiece respirators, an improvement in performance was found. The fifth percentile WPF without fit-testing is approximately 2 and with fit-testing is approximately 25 to 30. These results are very similar to those found in the NIOSH study. Summary While the NIOSH study may not predict actual workplace performance, from a comparative viewpoint, it illustrates the benefit of fit-testing. It indicates that screening people with a fit-test is useful for identifying those with poor-fitting respirators. If an OSHA-accepted method of fit-testing had been used, the increase in respirator performance may have been even greater. Based on the data reviewed above, we can conclude it is beneficial to perform fit-testing prior to respirator assignment. A decrease in total filter penetration in the laboratory and workplace has been shown when fit-testing is conducted. References 1. Centers for Disease Control. Laboratory Performance Evaluation of N95 Filtering Facepiece Respirators, 1996. Morbidity and Mortality Weekly Report 1998/47(48):1045-1049. 2. Myers, W. R., M. Jaraiedi, and L. Hendricks: Effectiveness of Fit Check Methods on Half Mask Respirators. Appl. Occup. Environ. Hyg. 10(11): 934-942 (1995). 3. "Respiratory Protection," Code of Federal Regulations Title 29, Part 1910.134. 1998. pp. 412-437. 4. American National Standards Institute. American National Standard for Respiratory Protection (ANSI Z88.2-1992). New York: American National Standards Institute, Inc., 1992. 5. NIOSH Respirator Decision Logic. US Dept. of Health and Human Services/National Institute for Occupational Safety and Health Pub. No. 87-108. pp. 29. 1987. 6. Gaboury, A., D. H. Burd, and R. S. Friar: Workplace Protection Factor Evaluation of Respiratory Protective Equipment in a Primary Aluminum Smelter. Appl. Occup. Environ. Hyg. 8(1):19-25 (1993). 7. Colton C. E. and J. O. Bidwell: "A Comparison of the Workplace Performance of Two Different Types of High Efficiency Filters on Half Facepiece Respirators." Paper presented at the 1995 American Industrial Hygiene Conference, Kansas City, MO, May, 1995. 8. Colton, C. E. , J. O. Bidwell, and H. E. Mullins: "Workplace Protection Factors of a Half-Facepiece High Efficiency Respirator in Different Environments." Paper presented at the 1994 American Industrial Hygiene Conference, Anaheim, CA, May, 1994. 9. Dixon, S.W. and T. J. Nelson: Workplace Protection Factors for Negative Pressure Half-Mask Facepiece Respirators. J. Int. Soc. Respir. Prot. 2(4):347-361(1984). 10. Galvin K., S. Selvin, and R. C. Spear: Variability in Protection Afforded by Half-Mask Respirators Against Styrene Exposure in the Field. Am. Ind. Hyg. Assoc. J. 51:625-639 (1990). 11. Colton, C. E., A. R. Johnston, H. E. Mullins, C. R. Rhoe and W. Myers: "Respirator Workplace Protection Factor Study on a Half Mask Dust/Mist Respirator." Poster presented at the 1990 American Industrial Hygiene Conference, Orlando, FL, May, 1990. 12. Zhuang, Z. and W. R. Myers: Field Performance Measurements of Half-Facepiece Respirators--Paint Spraying Operations. Am. Ind. Hyg. Assoc. J. 57:50-57 (1996). 13. Nelson, T. J. and S. W. Dixon: "Respirator Protection Factors for Asbestos, Parts I and II." Paper presented at the 1985 American Industrial Hygiene Conference, Las Vegas, NV, May, 1985. 14. Gosselink, D. W., D. P.Wilmes, and H. E.Mullins: "Workplace Protection Factor Study for Airborne Asbestos." Paper presented at the 1986 American Industrial Hygiene Conference, Dallas, TX, May, 1986. 15. Myers, W. R., Z. Zhuang and T. Nelson: Field Performance Measurememnts of Half-facepiece Respirators--Foundry Operations. Am. Ind. Hyg. Assoc. J. 57:166-174 (1996). 16. Myers, W. R. and Z. Zhaung: Field Performance Measurements of Half-Facepiece Respirators--Steel Mill Operations. Am. Ind. Hyg. Assoc. J. 59:789-795 (1998). 17. Colton, C. E.and H. E. Mullins: "Workplace Protection Factors for a Half Mask Dust/Mist/Fume Respirator." Poster presented at the 1992 American Industrial Hygiene Conference, Salt Lake City, UT, May, 1992. 18. Lenhart, S.W. and D. L. Campbell: Assigned Protection Factors for Two Respirator Types Based Upon Workplace Performance Testing. Ann. Occup. Hyg. 28(2):173-182 (1984). 19. Hery, M., J. P. Meyer, M. Villa, G. Hubert, J. M. Gerber, G. Hecht, D. Franc and J. Herrault: Measurement of Workplace Protection Factors of Six Negative Pressure Half-Masks. J. Int. Soc. Respir. Prot. 11(3):15-38 (1993). 20. Hery, M. V., G. Hubert and P. Martin: Assessment of the Performance of Respirators in the Workplace. Ann. Occup. Hyg. 35(2):181-187 (1991). 21. Fergin, S. G.: Respirator Evaluation for Carbon Setters with Beards. Am. Ind. Hyg. Assoc. J. 45(8):533-537 (1984). 22. Cohen, H. J.: Determining and Validating the Adequacy of Air-Purifying Respirators Used in Industry Part I--Evaluating the Performance of a Disposable Respirator for Protection Against Mercury Vapor. J. Int. Soc. Respir. Prot. 2(3):296-304 (1984). Note: Fit-testing was not conducted in the studies discussed in References 19-22.

Reuse of organic vapor chemical cartridges By Craig E. Colton, C.I.H. Introduction One of the most significant changes in the new Occupational Safety and Health Administration (OSHA) Respiratory Protection standard, 1910.134, is the requirement to establish change schedules for chemical cartridges used for gases and vapors. Change schedules are often based on service life measurements or estimates. To best use service life information, it is necessary to understand how chemical cartridges work. This is especially important when organic vapor cartridges are used against volatile chemicals during more than one work shift. When these cartridges are not in use, chemicals may desorb from the carbon in the cartridges. Inappropriate reuse of the organic vapor cartridges can result in breakthrough occurring earlier than predicted by the service life estimate. For example, when an organic vapor cartridge has been used for chemicals that migrate through the cartridge during the storage or nonuse period, it should not be reused. The decision to reuse cartridges may have an impact on worker protection and a respiratory protection program. How cartridges work Chemical cartridges are used on respirators to help remove and reduce worker exposure to harmful gases and vapors in the workplace. There are several types of chemical cartridges. Specific designs exist for removal of organic vapors, ammonia, formaldehyde, mercury vapor, and acid gases, such as hydrogen chloride, chlorine and sulfur dioxide. All chemical cartridges consist of a container filled with a sorbent. A chemical cartridge sorbent is a granular porous material that interacts with (or captures) the gas or vapor molecule in order to clean the air. Typically, this sorbent is activated carbon or activated charcoal. Activated carbon is an amorphous form of carbon characterized by high adsorptivity for many gases and vapors. Obtained by destructive distillation of wood, nutshells, animal bones or other carbonaceous material, activated carbon for respirators usually comes from coconut shells or coal. It is 'activated' through heating to 800-900 degrees celsius with steam or heat, which results in a porous internal structure, similar to that of a honeycomb. The internal surface area of activated carbon averages 10,000 square feet per gram and makes activated carbon ideal for removal of organic vapors by adsorption. Adsorption is the adherence of gas or vapor molecules to the surface of the activated carbon. The attractive force between the activated carbon and the chemical molecule is a relatively small, weak physical force. The strength of the attraction depends in part on the chemical. Since only weak physical forces are involved, the process can be reversed. This is called desorption. Desorption is the process by which an adsorbed material "lets go of" the activated carbon. Desorption can occur naturally during periods of nonuse or by the presence of another, more strongly adsorbed substance displacing a less strongly adsorbed chemical (i.e., a more volatile chemical). Generally, the more volatile the chemical, the less strongly adsorbed or the more likely it will undergo desorption. Desorption during storage or nonuse times can result in chemical migration. Migration is the movement of a previously adsorbed chemical through the chemical cartridge, even without air movement. Variables that appear to impact migration include: • Volatility -- the more volatile the chemical, the greater the concern for migration; • Water vapor coadsorption -- coadsorption [from use in atmospheres with high relative humidity (>50%)] can increase the migration effect; • Amount of material adsorbed onto the cartridge during the first use; • Storage time; and • Vapor type.(1) Concerns about desorption and migration The potentials for desorption and migration make reuse of organic vapor cartridges a concern. Not only are the more volatile chemicals more likely to desorb, but the capacity of the carbon is generally lower for these chemicals. This is true for many inorganic gases and organic vapors. In the case of organic vapors, in Europe, the more volatile chemicals are considered to be those that have boiling points less than 65 degrees celsius.(2) These chemicals are often classified as low boiling chemicals. Typical organic vapor cartridges would be expected to have lower capacity for these materials and desorption could be a major concern. Carbon capacity for inorganic gases can be increased and desorption of inorganic gases can be prevented by the use of special cartridges. To make cartridges more selective for certain chemicals such as inorganic gases and organic gases such as formaldehyde, sorbents can be impregnated with chemical reagents. Impregnated activated carbon removes specific gas and vapor molecules by chemisorption. Chemisorption is the formation of bonds between molecules of the carbon impregnant and the chemical contaminant. These bonds are much stronger than the attractive forces of physical adsorption. Binding is usually irreversible. Typically, reuse of chemical cartridges that utilize the principle of chemisorption should not pose a problem. Table 1 shows types of chemical cartridges and the mechanisms they use for removal of gases or vapors. The table indicates that organic vapor chemical cartridges that rely on adsorption as a removal mechanism are those for which desorption and migration present the biggest concern. In combination chemical cartridges that remove organic vapors, (e.g., organic vapors and acid gases or the multigas cartridge), the organic vapors are predominantly removed by adsorption. Reuse of organic vapor cartridges Caution needs to be exercised in establishing a change schedule when organic vapor cartridges are used for the following chemical exposures then reused: • Volatile chemicals that are likely to desorb during nonuse; • Two or more different chemicals adsorbed sequentially and one of the chemicals adsorbed later is more strongly adsorbed. Reuse with volatile chemicals When a chemical cartridge is used, the vapor collects on the first layers of carbon in the cartridge. During the period of nonuse, the chemical, depending upon its volatility and other conditions, may desorb and redistribute itself from areas of high concentration to areas of lower concentration, i.e., the back layers of carbon where no vapor has been collected. Eventually the chemical will reach the back of the cartridge. When it desorbs from the back of the cartridge, it goes into the air. This can result in workers breathing the chemical vapor when they put on their respirators initially, and potentially for some time thereafter, even if they are not in a contaminated area.(3) Reuse in a different environment Less volatile chemicals can cause desorption and subsequent early breakthrough of poorly adsorbed, more volatile chemicals. For example, a maintenance worker wears a respirator for exposure to chemical A. The use period is shorter than the service life for chemical A so no breakthrough occurs. The next day, the worker goes to another area and is exposed to a different organic chemical, chemical B, which is less volatile than chemical A. Since the service life was not fully used with chemical A, the organic vapor cartridges are reused. Before chemical B breaks through, it displaces the more volatile chemical A. If the change schedule does not consider this effect, chemical A may break through, thereby exposing the worker to chemical A. Laboratory studies have shown a more strongly adsorbed chemical can displace a relatively weakly adsorbed chemical.(4) This may result in a breakthrough concentration that exceeds the concentration in the air. While this study was conducted with simultaneous exposures of chemicals (mixtures), the same effect is very likely to occur from sequential exposures to two chemicals. For a maintenance worker, a compliance officer or other employee, who may use an organic vapor respirator in different environments, reuse may not be appropriate under any situation. Table 1 Chemical cartridge types and removal mechanisms Chemical Cartridge Type Removal Mechanism Examples of Impregnant Organic Vapors Adsorption N. A. Ammonia/Methylamine Chemisorption Nickel chloride, Cobalt salts, Copper salts, Acids Acid Gases Chemisorption Carbonate salts, Phosphate salts, Potassium hydroxide, Copper oxide Formaldehyde Chemisorption Copper oxide + metal sulfates, Salts of sulfamic acids Mercury Vapor Chemisorption Iodine, Sulfur Hydrogen Fluoride Chemisorption Carbonate salts, Phosphate salts, Potassium hydroxide, Copper oxide 3M™ Service Life Software 3M™ Service Life Software uses a method developed by Wood to determine service life for organic vapor cartridges by modeling the adsorption capacity and rate of adsorption of organic vapors from organic liquids.(5) The service life estimate is the time a cartridge would last until the selected breakthrough point is reached. For organic vapors, it is the time cartridges would be expected to last with a single continuous use. In other words, a service life estimate of 16 hours means it would last 16 hours if used continuously under the conditions of the estimate. It does not necessarily mean that it will last two 8-hour shifts when stored overnight. For nonvolatile chemicals, 3M studies indicate service life is very close to the estimate even with periods of nonuse. This is not true for more volatile chemicals. 3M Service Life Software uses boiling points less than 65 degrees celsius to identify highly volatile chemicals. Many of the service life estimates for more volatile chemicals will be shorter due to the lower capacity of carbon for these chemicals. Some, however, may be longer than 8 hours. When a service life estimate is made for a low boiling chemical, a warning is shown that advises the chemical cartridge be disposed of after the shift even if the service life estimate is longer than 8 hours. This is because these chemicals are likely to desorb and migrate throughout the cartridge during short periods of nonuse (i.e., a few hours to overnight). However, the boiling point of 65 degrees celsius is not a fine line between chemicals that desorb and those that do not. Boiling point can be misleading for chemicals that undergo hydrogen bonding, such as alcohols. Hydrogen bonding results in a higher boiling point than would be expected based on molecular weight. Chemicals with higher boiling points can still desorb and migrate, however, it may take slightly longer to occur. Experiments with ethyl acetate (BP = 77 degrees celsius) have shown significant desorption after 63 hours of storage (nonuse).(1) For this chemical, reuse after a short nonuse period may be acceptable, but reuse after a weekend probably should not be attempted. Change-out schedule recommendations Unfortunately, little information has been published for evaluating the effect of desorption or migration on cartridge service life. The two safest approaches when the service life estimate is longer than the use period are: • Never reuse an organic vapor chemical cartridge; dispose of it after the period/shift in which it is used. • Conduct desorption studies in a laboratory, mimicking the conditions of use/reuse at your work site. Use these data when establishing the change schedule. The ANSI Z88.2-1992 standard recommends desorption studies unless cartridges are changed daily.(6) OSHA states, in its compliance directive, that where contaminant migration is possible (chemicals with boiling points below 65 degrees celsius), respirator cartridges should be changed after every work shift where exposure occurs.(7) If the employer has specific objective data (desorption studies) showing the performance of the cartridge under the conditions and schedule of use/nonuse found in the workplace, daily change would not be required. Using 65 degrees celsius as the indicator for migration does not take into account those materials that may migrate after slightly longer periods of nonuse. Therefore, in the future, one could consider establishing guidelines for reuse based on the volatility of the chemical. Three or four levels of volatility could be established. Different periods of nonuse would be acceptable for highly volatile chemicals, moderately volatile chemicals and low volatility chemicals. No guidelines are presently available to indicate which boiling points, or other indicator of volatility, should be used as the cutoff between moderate and low volatility. As volatility increases, reuse of cartridges for organic vapors should be restricted, specifically: • Cartridges used for organic chemicals that are very volatile should never be reused. For example, cartridges exposed to chemicals with boiling points less than 65 degrees celsius should never be used for more than one shift. • Cartridges used for chemicals of moderate volatility should never be reused after a few days of nonuse. For example, never reuse the cartridge if the cartridge change schedule results in storage over a weekend. • Cartridges for chemicals of low volatility that are used for some longer period of time that is still less than the service life estimate should never be reused. For example, cartridges used for these types of organic chemicals should never be used longer than one or two weeks. For use with mixtures of chemicals, the acceptable nonuse or storage period should probably be based on the most volatile component of the mixture. In the future, as more information becomes available, firm recommendations about reuse can be made. Conclusion Before setting a cartridge change schedule, the volatility of the chemical, the cartridge use/nonuse patterns, and desorption data (if available) should all be evaluated. If desorption data are not available, the prudent practice is to never reuse organic vapor cartridges when the service life estimate is greater than one work shift. For organic chemicals that migrate through the cartridge during the storage or nonuse period, the organic vapor cartridge must not be used for more than one work shift. References 1. Wood, G. and R. Kissane.: Reusability of Organic Vapor Air-Purifying Cartridges. Los Alamos National Laboratory. 1998. 2. Balieu, E.: Respirator Filters in Protection Against Low-Boiling Compounds. J. International Soc. for Respiratory Protection 1:125-138 (1983). 3. Moyer, E. S.: Review of Influential Factors Affecting the Performance of Organic Vapor Air-Purifying Respirator Cartridges. Am. Ind. Hyg. Assoc. J. 44(1):46-51 (1983). 4. Yoon, Y. H., J. H. Nelson and J. Lara.: Respirator Cartridge Service-Life: Exposure to Mixtures. Am. Ind. Hyg. Assoc. J. 57(9):809-819 (1996). 5. Wood. G. O.: Estimating Service Lives of Organic Vapor Cartridges. Am. Ind. Hyg. Assoc. J. 55(1):11-15 (1994). 6. American National Standards Institute. American National Standard for Respiratory Protection (ANSI Z88.2-1992). New York: American National Standards Institute, Inc., 1992. 7. US DOL/OSHA. Inspection Procedures for the Respiratory Protection Standard (CPL 2-0.120). Washington, D. C.: US Department of Labor/Occupational Safety and Health Administration, September 18, 1998.

New 3M Service Life Software available free Web-Based Version Downloadable Version

3M™ Service Life Software Version 2.0 offers new features 3M has introduced new features and improvements to its software that helps calculate end of service life for 3M organic vapor respirator cartridges. 3M™ Service Life Software Version 2.0 is available in web-based and downloadable versions. It also is integrated with 3M Select Software©. Version 2.0 has these new features: • Mixtures: Enter mixtures of organics, inorganics or both • User-entered contaminants: Enter your own organic vapor contaminants • New contaminants: Several inorganics and organic gases are now available: - Ammonia - Hydrogen fluoride - Hydrogen sulfide - Methylamine - Sulfur dioxide • Correction factors: Enter user-selected correction factors to account for uncertainties • Humidity: Access information about humidity effects and suggested correction factors to account for the effects. It also calculates service life based on workplace conditions such as contaminant concentration, temperature, work rate and atmospheric pressure. This software offers users an easy method for calculating end of service life for 3M respirator cartridges. Cartridge service life is the estimated period of time before breakthrough under specific conditions. This information can be used to establish an appropriate change schedule. The recently revised OSHA respiratory protection standard, 29 CFR 1910.134, requires users of chemical cartridge respirators to implement a cartridge change schedule based on "objective information or data" to help prevent worker overexposure. OSHA believes that chemical odor "breakthrough" is no longer an adequate indicator of when to change cartridges. 3M's Service Life Software is based on a model developed by G.O. Wood and published in the American Industrial Hygiene Association Journal, January 1994. An appropriate cartridge change schedule is one that is both convenient and assures that the concentration of the chemical downstream does not exceed the exposure limit. For example, a cartridge may have a breakthrough time of 15 hours for a given vapor. Changing cartridges at the end of a normal work shift is convenient, and this period of use is less than the breakthrough time. Several methods can be used to estimate breakthrough times (i.e. service life). These vary in cost, complexity and precision. All methods require professional judgment to establish an appropriate change schedule and all require the same basic information.

Do I need a respiratory protection program if...? Voluntary use and related issues By Larry L. Janssen, C.I.H. Larry Janssen is a Certified Industrial Hygienist with the 3M OH&ESD Laboratory. Since it was first published in 1971, the Occupational Safety and Health Administration (OSHA) respiratory protection regulation, 29 CFR 1910.134, has listed the elements of a respiratory protection program. The program elements include: • Proper respirator selection; • Training; • Fit-testing; • Medical evaluation; • Maintenance procedures, including cleaning, inspection, repair and storage; • Procedures for proper respirator use; • Breathing air quality assurance for atmosphere supplying respirators; • Program evaluation. These elements are intended to maximize respirators' ability to reduce air contaminant exposures and to assure that misuse of respirators does not create hazards for users. Exposures below the PEL OSHA has always required employers to have a complete respiratory protection program when respirators are used to protect employees from air contaminant exposures above the OSHA Permissible Exposure Limit (PEL). However, respirators are often used in two situations in which the PEL is not exceeded: 1. When employer policy requires respirator use for specific operations; 2. When employees ask to wear respirators, and the employer permits their use, i.e., voluntary respirator use. It should be emphasized that exposure assessment (preferably air sampling) is necessary to determine whether overexposures exist. OSHA specifies requirements OSHA's original respiratory protection regulation did not identify respiratory protection program requirements for situations in which there is no overexposure. However, the January 8, 1998 revision to 1910.134 specifies the respirator program elements that are necessary when respirators are used for exposures below the PEL. When employer policy requires respirator use, the program requirements are stated very simply: all elements of a respiratory protection program must be in place. An employer's decision to require respirator use indicates a belief that a hazard may exist although the OSHA PEL is not exceeded. For example, the employer may decide to control exposures to a lower, advisory exposure limit, such as the Threshold Limit Value (TLV®). It clearly makes sense to maximize respirator effectiveness with a complete respiratory protection program, since protection from a perceived hazard is intended. Voluntary use Before discussing OSHA's program requirements for voluntary respirator use, it is important to state clearly what voluntary use is and is not. Voluntary use means that: • An exposure assessment has been conducted; • The PEL is not exceeded; • No OSHA regulation requires that respirators be provided by the employer (For example, 1910.1025, requires employers to provide respirators upon request to employees exposed to lead at any concentration); • The employer does not believe it is necessary to reduce exposures below their current levels, i.e., there is no perceived hazard; • The employer does not require, recommend, encourage or suggest that respirators be used; • Workers ask to wear respirators; • The respirators will not be used for emergency response or escape. If one or more of these conditions are not met, respirator use is not voluntary; a complete respiratory protection program is required. If respirator use is permitted and all of the above conditions are met, a voluntary use situation exists. Paragraph (c)(2) of 1910.134 requires a limited respiratory protection program in this case. The only program elements specified are those that OSHA believes will prevent respirator use from creating a hazard to the user. These are: • Medical evaluation, principally because the breathing resistance associated with negative pressure respirators may be intolerable to a few individuals; • Cleaning, storage and maintenance, because a respirator contaminated by improper storage and/or not cleaned could promote skin irritation or similar problems; and • Minimal training, i.e., the information found in Appendix D of the regulation. A puzzling exemption Interestingly, for voluntary use of filtering facepiece respirators, which OSHA also calls dust masks, the regulation contains an exemption from two of these program requirements. Workers who wear filtering facepieces voluntarily need only be provided with the information in Appendix D. This exemption is puzzling for the following reasons: • A filtering facepiece of a given class, e.g., P100, has approximately the same breathing resistance as the same filter type used in an elastomeric facepiece; • A filtering facepiece that is stored improperly could become contaminated and cause the same problems that a contaminated elastomeric facepiece can cause; • When use of filtering facepieces is required because of overexposure or employer policy, the situation is handled in exactly the same manner as with any other respirator: a complete respiratory protection program is required. For these reasons, filtering facepieces and other respirators should not be treated differently in voluntary use situations. The same program elements that are appropriate for elastomeric respirators should be implemented for filtering facepieces. Consider additional program elements Finally, employers must decide if OSHA's voluntary use program requirements are sufficient for voluntary use in their workplaces. Additional program elements should be considered in many situations. The following two examples illustrate this point: 1. OSHA does not require procedures for proper respirator use in voluntary situations. This omission permits misuse, such as wearing a beard with a tight-fitting respirator. This practice is prohibited when respirator use is required. At the very least, allowing voluntary respirator users to have beards would cause administrative problems if workers in another part of the facility are required wear respirators and be clean-shaven. For this reason, (and others; see example 2) many employers may choose to require voluntary respirator users to be clean-shaven. 2. Fit-testing is not required for voluntary use. Employers must determine if waiving fit-testing is compatible with their reasons for allowing respirators to be used voluntarily. If the goal of voluntary use programs is enhancing employees' comfort, with the full understanding that there is no real or potential hazard present, employers may be comfortable not requiring fit-testing. Specifically, a non-hazardous atmosphere leaking into the facepiece is not a concern. Conversely, employers who believe that exposures should be reduced to the lowest possible level, even when there is no known hazard, will include fit-testing in their voluntary use programs. Given the litigious nature of our society, many employers will no doubt conclude that it is prudent to maximize respirators' effectiveness whenever they are used. If so, they will elect to implement complete respiratory protection programs for voluntary use. TLV is a registered trademark of the American Conference of Governmental Industrial Hygienists.

3M OH&ESD announces training courses for 2000 Are you interested in learning the latest available information on establishing a cartridge change schedule? Do you want hands-on experience in analyzing breathing air quality? Are you an experienced respirator program administrator who just needs to know "3M Canada Occupational Health and Safety What's New" in respiratory protection regulations and technology? 3M has a unique program to respond to these and many more professional development requirements. Two training courses are offered to provide individuals involved with a respirator program the information they need to operate their program effectively. The courses are unique among those offered by respirator manufacturers in that they are based on the technical and regulatory aspects of a sound respirator program rather than specific products. In fact, a large equipment display from a number of respirator manufacturers is used to supplement the classroom and workshop presentations. Respiratory Protection is a comprehensive four and one-half day course intended for anyone involved with managing all or part of a respiratory protection program. All respirator types and each element of a respirator program are thoroughly discussed. Workshop sessions are used extensively to reinforce the course material. Current Topics in Respiratory Protection is a two-day course designed to provide the latest in technical and regulatory information to experienced program managers. The schedule of course locations and dates for 2000 is listed below. To find out more about these courses, do one of the following: • Contact your 3M Sales Representative; • Phone 1-800-659-0151, ext. 275; • Visit our web site at www.3M.com/occsafety; • Dial the 3M Fax On Demand system at 1-800-646-1655. Respiratory Protection San Diego, CA January 24-28 Williamsburg, VA March 13-17 Nashville, TN April 10-14 Minneapolis, MN July 10-4 Seattle, WA September 11-15 Phoenix, AZ October 23-27   Current Topics in Respiratory Protection Nashville, TN April 17-18 Minneapolis, MN July 17-18     Tech line To reach 3M's Technical Service staff with questions regarding our products, you can call 1-800-243-4630. If you wish to contact your local sales representative, you can leave a message by calling 1-800-896-4223.