Safety Tidbit 4.15 - Quantitative Fit-testing

Safety Tidbit 4.15 – Quantitative Fit-testing

Reference:       OSHA Respiratory Protection Standard (1910.134)

When providing respiratory protection in the workplace, you must choose the level of protection based on the exposure level. When using air-purifying respirators, OSHA has assigned protection factors of 10 and 50 for half-face and full-face respirators respectively. Meaning the respirator are not to be used where ambient concentrations exceed 10 or 50 times the permissible exposure limit (PEL). Also, the employer must fit-test the worker annually to ensure they use their respirator correctly and challenge them with a test agent.

There are four (isoamyl acetate, Bitrex^TM, saccharin mist, and irritant smoke) qualitative protocols that OSHA recognizes and explains in Appendix A of the federal respiratory protection standard. Ultimately, each protocol relies on feedback from the worker whether they detect the test agent or not. As an old-school industrial hygienist, I like irritant smoke since it usually elicits an involuntary response of coughing from the worker. However, Bitrex, which uses the chemical (denatonium benzoate) found in some commercial products to make their flavor undesirable to children, generally producing a slight involuntary response. Although the fit-tester must be paying attention to catch the worker’s “tell” or involuntary response.

Quantitative fit-testing requires no interpretation from the worker. There are two quantitative fit-testing protocols – ambient aerosol and controlled negative pressure. Ambient aerosol compares the level of aerosols outside the mask that within the mask to determine the fit of the respirator. Controlled negative pressure places a slight negative pressure on the mask to determine leakage. Each has its pros and cons – a major con being the price of the units themselves.

Interestingly, to pass the quantitative fit-test method, a fit-factor of 100 for half-face respirators and 500 for full face respirators are required. So, I ask, can the worker now wear the respirator in environments with ambient concentrations of 100 or 500 times the permissible exposure limit? The answer is NO. The levels required are to pass the quantitative fit-test method. A half-face air-purifying respirator is only to be used in ambient concentrations up to 10 times the permissible exposure limit and full-face respirators only up to 50 times the PEL.

Hope this was helpful and thank you for reading my Safety Tidbits! Comments and questions are always welcome. ~ Bryan

P.S. If you have a new safety or health question, please let me know.