Fit Testing Procedures
Regulations
Within the standard, employers are provided the option of conducting either a quantitative or qualitative fit test. The individual performing the fit test procedure requires no special certification. However, the individual must be able to prepare the test solutions, calibrate the equipment and perform the tests properly, recognize invalid tests, and ensure that test equipment is in proper working order. The ability to calculate fit factors is also a requirement for the individual administering a quantitative fit test (QNFT).
As defined in the standard, a QNFT means "an assessment of the adequacy of respirator fit by numerically measuring the amount of leakage into the respirator." A QNFT is necessary for respirators that must achieve a fit factor of greater than 100. This would be an atmosphere-supplying respirator that's being used in an environment where the airborne concentration of a contaminant is more than 100 times the OSHA permissible exposure limit (PEL).
A QNFT uses an instrument to take a sample from within the wearer's breathing zone while the respirator is being worn. In addition to the instrument, a challenge agent and a probed respirator (or probed adapters for a standard respirator) are necessary to perform a QNFT. A QNFT is more precise than a qualitative fit test; it's also less commonly performed because of the complexity of the procedure and the prohibitive cost of the analyzation instrument. The protocol for a QNFT is detailed in Appendix A, subpart C to 29 CFR 1910.134.
The standard defines a qualitative fit test (QLFT) as "a pass/fail fit test to assess the adequacy of respirator fit that relies on the individual's response to the test agent." A QLFT, according to 29 CFR 1910.134(f)(6), "may only be used to fit test negative pressure air-purifying respirators that must achieve a fit factor of 100 or less."
The downside to a QLFT is that it relies upon the subjective response of the individual being tested, so that reproducibility and accuracy may vary. The upside is that a QLFT is simpler to perform than a QNFT; the necessary testing equipment is also more accessible and economical.
Within appendix A of the standard, the following four acceptable QLFT protocols are defined: Isoamyl Acetate (more commonly known as banana oil), Saccharin Solution Aerosol, Bitrex Solution Aerosol, and Irritant Smoke (Stannic Chloride).
The test method performed will dictate the type of air-purifying element that's used on the face piece. The isoamyl acetate QLFT requires respirators equipped with organic vapor cartridges. Both the saccharin and bitrex QLFT require respirators equipped with particulate filters (either 95, 99 or 100 series filters are acceptable). To perform the irritant smoke test, the respirator needs to be equipped with either a P100 series particulate filter or HEPA filter.
It's important to note that when performing the irritant smoke test, no form of enclosure or hood for the test subject is to be used. The other QLFTs all require the use of an enclosure. Complete instructions for all QLFTs are detailed within appendix A to 29 CFR 1910.134.
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