There is often little or no information available with which to determine whether adequate warning properties exist for new chemical substances. In addition, there is often considerable uncertainty regarding the potential human health effects for new chemicals. Finally, odor threshold data as reported in the literature has been found to vary considerably due to the type of data source, the characteristics of human olfactory response, and differences in experimental methodology⁽¹⁾, Due to these uncertainties, the Agency has determined that odor threshold or other testing to identify warning properties is not warranted. Instead, service life testing of organic vapor cartridges or canisters for the new chemical substance during the anticipated conditions of exposure and a cartridge change out schedule determined on the basis of the testing, is required.

There are many factors that affect cartridge service life, such as temperature, relative humidity, challenge concentration, and other environmental and use factors^(2-6). In addition, other contaminants can greatly influence the performance of the cartridge and should be considered when conducting cartridge service life testing. While there is no standard test methodology for determination of organic vapor cartridge service life, a testing protocol was published in a peer reviewed technical journal⁽⁷⁾. The performance of an organic vapor respirator cartridge in removing a selected airborne substance via adsorption or chemical reaction can be determined by measuring the breakthrough time of the substance through the cartridge under various test conditions.

Summary of Method. These Interim Recommendations for performing organic vapor cartridge service life testing are based on recommendations presented in the published article⁽⁷⁾, a draft Decision Logic prepared by NIOSH for the EPA⁽⁸⁾, and professional judgment. The current recommendations require at least 8 tests during the PHASE I testing. Depending on the use conditions, additional testing may be required in PHASE II to investigate desorption characteristics at elevated temperatures. Specific requirements for PHASE II testing will be established by EPA on a case-by-case basis, although it is anticipated that testing at elevated temperatures will be necessary for many new chemicals substances.

The testing protocol represent reasonable worst case environmental testing conditions and minimum testing requirements; companies are encouraged (but not required) to perform additional testing to more fully characterize the sorbent/contaminant breakthrough characteristics⁽⁷⁾. The safety factor of 60% of the cartridge service life for field application has been retained from Revision 1 to account for variability between laboratory measurements and actual field performance. These recommendations apply only to cartridges and canisters approved by NIOSH/MSHA under 30 CFR 11. As NIOSH modifies the certification standards and adopts 42 CFR 84, these requirements will be reevaluated.

In April, 1994, the Industrial Hygiene Task Group of the Chemical Manufacturers Association (CMA) submitted suggested changes to the Revision 1 Interim Recommendations (dated May 1, 1991)⁽⁹⁾. The CMA Industrial Hygiene Task Group in February, 1995 again stated their preference for a protocol consisting of a single set of tests at the maximum use concentration for the cartridge under the reasonably anticipated worst case environmental conditions⁽¹⁰⁾. Testing would be done in triplicate, with a demonstrated excess service life of 50%. Furthermore, the CMA stated that the EPA protocol was excessive and was more reflective of a research protocol. EPA carefully reviewed the recommendations, consulted with experts at Los Alamos and NIOSH, reviewed the available literature, and responded to the CMA comments in a joint letter with NIOSH dated May, 1994⁽¹¹⁾. EPA revised the Interim Recommendations accordingly. While EPA strongly supports reducing testing costs while still maintaining acceptable worker protection, EPA believes that it is necessary to test at more than one concentration, humidity, and temperature to determine the reasonably anticipated worst case conditions. For example, low relative humidity, rather than high, may be worst case conditions for some substances, and the same is true with temperature. The CMA suggestions are a viable option only if it can be demonstrated that the selected environmental conditions are indeed worst case; EPA knows of no reliable means of demonstrating this without testing. The EPA Interim Recommendations are subject to modification on a case by case basis, and companies are encouraged to carefully evaluate the protocol as it applies to their case and consult with EPA as needed.

Testing Protocol.

Section 1. Initial Screening for Cartridge or Canister Service Life.

Several models have been developed for predicting organic vapor cartridge service life^(12-23). However, their applicability for predicting cartridge service life for untested compounds is limited, especially for new chemical substances where data useful in predicting service life (e.g. vapor pressure, capacity and adsorption rate, etc.) is generally limited or unavailable. Recently, a model was published based on the modified Wheeler equation and incorporated advancements in predicting organic vapor cartridge service life for untested compounds, provided minimal information on the challenge compound and on the adsorption carbon were available⁽²⁴⁾. However, the model currently only considers dry conditions (relative humidity < 50%).

Predictive models can be useful to initially screen whether a cartridge might be appropriate for a new chemical substance. If the model predicts service life at less than 20 minutes for the new chemical substance, then an organic vapor cartridge may not be appropriate for the substance, and the company may want to reconsider the use of a supplied-air respirator instead of performing cartridge service life testing on cartridges or canisters.

Section 2. High Heats of Reactions with the Sorbent.

The company shall document that the new chemical substance will not result in high heats of reaction (> 20°C above ambient temperature) with the sorbent material of the cartridge or canister. For substances which generate high heats of reaction, only non-oxidizing sorbent materials shall be used.

Section 3. Preparation of Cartridges or Canisters for Testing.

Cartridges and canisters shall be tested as received (dry bed conditions). Cartridges used in pairs on an air-purifying respirator should be tested in parallel in pairs, or the airflow rates should be halved for testing them singly.

Section 4. Testing Parameters for Cartridge or Canister Service Life Testing.

The minimum required replicates and testing parameters for performing cartridge and/or canister service life testing are:

PHASE I Testing Requirements

PHASE II testing requirements will be established on a case-by-case basis. At a minimum, if the cartridge and/or canister will be used as protection against inhalation exposure at elevated temperatures (> 35°C) , the following additional testing is required:

PHASE II Testing Requirements

^a Where x = New Chemical Exposure Limit (NCEL), or the predicted airborne concentration if no NCEL exists.

^b More than two replicates shall be tested if the variability between results for each set of replicates exceeds 10%.

^c If the results of PHASE I testing demonstrate that the service life under low (e.g. 20%) relative humidity conditions is less than the service life at 80% relative humidity, then PHASE II testing shall be conducted under low (20 ± 5%) relative humidity conditions instead of the higher relative humidity conditions specified.

Section 5. Cartridge Change Out Schedule.

The company shall establish a cartridge/canister change out schedule based on the results of the service life testing for reasonable worst case testing conditions, any administrative controls that will be used, and incorporating the safety factor of 60% of the measured service life to account for variability in environmental conditions. Cartridges or canisters shall be changed prior to the end of service life, or at the end of the shift, whichever comes first. The cartridge change out schedule and other administrative actions shall be incorporated into the Respiratory Protection Program, as required by 29 CFR 1910.134.

If extended cartridge change out schedules (longer than 1 work shift) are desired, the company should consult with EPA as additional testing will be required to demonstrate that desorption and migration of contaminant vapor between shifts and during repeated storage and reuse does not occur. There has been little or no research in this area, and standard testing protocols are currently unavailable.

Section 6. Reporting of Data.

The following data and information shall be submitted to EPA for review and approval of cartridge and/or canister service life testing data:

i) the actual breakthrough curve and the tabulated concentration versus time for each set of testing parameters;

ii) at a minimum, the breakthrough times at 1% and 10% of the vapor concentration shall be reported;

iii) information on the analytical method including, but not limited to the limit of detection, range of applicability, a description of the method, accuracy and precision, etc. shall be reported;

iv) the canister or cartridge specifications should be reported in as much detail as is available;

v) the cartridge change out schedule and any administrative actions incorporated into the Respiratory Protection Program shall be reported; and

vi) documentation that the new chemical substance will not result in high heats af reaction (> 20°C above ambient temperature) with the sorbent material of the cartridge or canister.

Section 7. EPA Approval.

Upon receipt of EPA approval of the cartridge service life data and the cartridge change out schedule, the company may use NIOSH/MSHA approved air-purifying respirators equipped with an organic vapor cartridge or canister for protection against inhalation exposure to the new chemical substance instead of NIOSH/MSHA approved supplied-air respirators. The organic vapor cartridge used shall provide equivalent or greater sorption capacity to the cartridge or canister tested.

Section 8. Other Use Conditions.

The cartridge and/or canister is approved only for use in use conditions similar to those reflected by the testing parameters (e.g. single contaminant (the new chemical substance) at a range of airborne concentrations, low to high relative humidity, and selected ambient temperature(s)).

Organic vapor-acid gas cartridges and/or canisters may be used for protection against the new chemical substance provided the sorption capacity of the organic vapor-acid gas cartridge or canister is equivalent or greater than that of the tested cartridge or canister.

However, if there is potential for inhalation exposure to multiple contaminants (e.g. the new chemical substance and an acid gas), additional service life testing would be necessary to demonstrate that the cartridge or canister selected is appropriate. Only limited evaluation of the breakthrough characteristics of multiple contaminant systems has been conducted to date^(25-26).

REFERENCES

1. American Industrial Hygiene Association: Odor Thresholds for Chemicals with Established Occupational Health Standards. American Industrial Hygiene Association: Fairfax, VA. (1989).

2. Nelsen, G.O., and C.A. Harder: Respirator Cartridge Efficiency Studies: V. Effects of Solvent Vapor. Am. Ind. Hyg. Assoc. J. 35:391-410 (1974).

3. Moyer, E.S.: Review of Influential Factors Affecting the Performance of Organic Vapor Air-Purifying Respirator Cartridges. Am. Ind. Hyg. Assoc. J. 44:46-51 (1983).

4. Nelson, G.O. and A.N. Correia: Respirator Cartridge Efficiency Studies: VII. Summary and Conclusions. Am. Ind. Hyg. Assoc. J. 37:514-525 (1976).

5. Hall, T., P. Breysse, M. Corn, and L.A Jonas: Effect of Adsorbed Water Vapor on the Adsorption Rate Constant and the Kinetic Adsorption Capacity of the Wheeler Kinetic Model. Am. Ind. Hyg. Assoc. J. 49:461-464 (1988).

6. Nelson, G.O., A.N. Correia, and C.A. Harder: Respirator Cartridge Efficiency Studies: VII. Effect of Relative Humidity and Temperature. Am. Ind. Hyg. Assoc. J. 37:280-288 (1976).

7. Wood, G.O. and Ackley, M.W.: A Testing Protocol for Organic Vapor Respirator Canisters and Cartridges. Am. Ind. Hyg. Assoc. J. 50:651-654 (1989).

8. Bollinger, N. and Coffey, C.: Decision Logic for Organic Vapor Cartridge Respirators for Premanufacture Notification (PMN) Substances. DRAFT (May 25, 1988, unpublished).

9. Chemical Manufacturers Association. Letter to Mr. Gerry Wood, Los Alamos National Laboratory from Thomas J. Nelson, 3M, and Karen M. Cragg, CMA. (April 11, 1994).

10. Chemical Manufacturers Association. DRAFT Comments submitted to Mr. Roy Seidenstein, EPA from Mr. R. Holmes, on the proposed Generic Section 5(e) Order with New Chemical Exposure Limits, as a supplement to comments previously submitted. (February 6, 1995).

11. National Institute for Occupational Safety and Health. Letter to Ms. Karen M. Cragg and Mr. Thomas J. Nelson, Chemical Manufacturers Association from Ernest S. Moyer, Ph.D. and Cathy Fehrenbacher, EPA.

12. Smoot, D.M., Smith, D.L., and Scheh, T.A.: Development of Improved Respirator Cartridge and Canister Test Methods. U.S. Dept. of Health and Human Services, Public Health Service. Center for Disease Control. National Institute for Occupational Safety and Health. Publication No. 77-209.

13. Ackley M.W.: Residence Time Model for Respirator Sorbent Beds. Am. Ind. Hyg. Assoc. J. 46:679-689 (1985).

14. Yoon, Y.H. and J.H. Nelson: Application of Gas Adsorption Kinetics: I. A Theoretical Model for Respirator Cartridge Service Life. Am. Ind. Hyg. Assoc. J. 45:509-516 (1984).

15. Yoon, Y.H. and J.H. Nelson: Application of Gas Adsorption Kinetics: II. A Theoretical Model for Respirator Cartridge Service Life and Its Practical Applications. Am. Ind. Hyg. Assoc. J. 45:517-524 (1984).

16. Wood, G.O.: A Model for Adsorption Capacities of Charcoal Beds: II. Challenge Concentration Effects. Am. Ind. Hyg. Assoc. J. 48:703-709 (1987).

17. Yoon, Y.H. and J.H. Nelson: A Theoretical Study of the Effect of Humidity on Respirator Cartridge Service Life. Am. Ind. Hyg. Assoc. J. 49:325-332 (1988).

18. Wood, G.O.: A Model for Adsorption Capacities of Charcoal Beds. I. Relative Humidity Effects. Am. Ind. Hyg. Assoc. J. 48:622-625 (1987).

19. Moyer, E.S.: Organic Vapor (OV) Respirator Cartridge Testing - Potential Jonas Model Applicability. Am. Ind. Hyg. Assoc. J. 48:791-797 (1987).

20. G.O. Wood and E.S. Moyer: A Review of the Wheeler Equation and Comparison of Its Applications to Organic Vapor Respirator Cartridge Breakthrough Data. Am. Ind. Hyg. Assoc. J. 50:400-407 (1989).

21. Wood, G.O. and E.S. Moyer: A Review and Comparison of Adsorption Isotherm Equations Used to Correlate and Predict Organic Vapor Cartridge Capacities. Am. Ind. Hyg. Assoc. J. 52:235-242 (1991).

22. Wood, G.O.: Activated Carbon Adsorption Capacities for Vapors. Carbon 30:593-599 (1992).

23. Wood, G.O.: Organic Vapor Respirator Cartridge Breakthrough Curve Analysis. J. Int. Soc. Resp. Prot. Winter :5-17 (1992-93).

24. Wood, G.O.: Estimating Service Lives of Organic Vapor Cartridges. Am. Ind. Hyg. Assoc. J. 55:11-15 (1994).

25. Yoon, Y.H., J.H. Nelson, J. Lara, C. Kamel, and D, Fregeau.: A Theoretical Interpretation af the Service Life of Respirator Cartridges for the Binary Acetone/m-Xylene System. Am. Ind. Hyg. Assoc. J. 52:65-74 (1991).

26. Yoon, Y.H., J.H. Nelson, J. Lara, C. Kamel, and D. Fregeau.: A Theoretical Model for Respirator Cartridge Service Life for Binary Systems: Application to Acetone/Styrene. Am. Ind. Hyg. Assoc. J. 53:493-502 (1992).