Respirator Fit Testing Requirements
When OSHA's revised Respiratory Protection Standard, 29 CFR 1910.134, became effective on April 8, 1998, it provided employers with an all-inclusive reference source for fit testing guidelines. Before its revision, the standard made reference to testing a respirator's "face-piece-to-face seal," but provided no additional guidance on how to perform the test. The standard now specifies what needs fit testing, the kinds of fit tests allowed, the procedures for conducting them and how frequently fit tests must be performed.
29 CFR 1910.134(f) states, "Before an employee may be required to use any respirator with a negative or positive pressure tight-fitting facepiece, the employee must be fit tested with the same make, model, style and size of respirator that will be used." This statement is noteworthy because it mandates that tight-fitting positive pressure facepieces such as those used in PAPRs and airline respirators be fit tested. The statement also does not exclude disposable particulate respirators from fit testing. See Quick Tips #318: Quantitative Fit Testing.
Two methods are acceptable for fit testing a tight-fitting positive pressure mask:
- The mask can be converted into a negative pressure respirator and equipped with filters appropriate to the fit test protocol being followed, or
- An identical negative pressure respirator can be used as a surrogate for fit testing as long as it has the same sealing surfaces as the positive pressure respirator.
Fit Testing Procedures
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 10.
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 adapter 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 facepiece. 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.
Three Approved Methods for QNFT
- Generated Aerosol Booth System QNFT uses an aerosol mixture (commonly corn oil) administered in a test chamber or booth. The subject stands inside the booth or chamber and performs a series of exercises as the instrument samples how much challenge agent leaks into the respirator. This system is not widely used due to the high maintenance required to clean the equipment and the relatively large size of the system.
- Ambient Aerosol QNFT instruments measure aerosol concentrations inside and outside the test respirator and compute the fit factor. The challenge agents used in this test includes ambient microscopic dust in the air and other aerosols. Ambient aerosol fit testers use a technology referred to as condensation nuclei counting (CNC) or condensation particle counting (CPC). These testers use laser technology to count particles. The respirator used in the test is equipped with P100 (HEPA) filters that prevent the ambient particles from passing into the respirator. Accessories are also available to conduct a QNFT on lower class filters, such as the 95 class filters, commonly found in disposable filtering facepiece respirators. One of the more common ambient aerosol fit testers is the TSI Portacount.
- Controlled Negative Pressure (CNP) QNFT involves the instrument pulling affixed vacuum on the respirator and the instrument measuring the airflow, or leak rate, needed to maintain the vacuum. There are two drawbacks to this type of testing: 1) the subject must hold their breath and remain motionless during the measurement, and 2) CNP testing cannot be performed with filtering facepiece respirators.
Advantages of QNFT vs. QLFT
There are several advantages to QNFT:
- QNFT is an objective test and eliminates the subjectivity of a persons sense of smell, taste and sensitivity to challenge agents.
- QNFT is suitable for determining higher levels of fit that may be required for full-face, gas masks, or other respirators.
- QNFT provides faster, more precise and hard copy documentation of the instrument results.
- QNFT eliminates the chances of deception often found in QLFT.
29 CFR 1910.134(f)(2) states, "The employer shall ensure that an employee using a tight-fitting facepiece respirator is fit tested prior to initial use of the respirator, whenever a different respirator facepiece (size, style, model or make) is used, and at least annually thereafter." In addition, fit testing must be repeated "whenever the employee reports, or the employer, PLHCP (physician or other licensed healthcare professional), supervisor, or program administrator makes visual observations of changes in the employee's physical condition that could affect respirator fit. Such conditions include, but are not limited to, facial scarring, dental changes, cosmetic surgery, or an obvious change in body weight."
Also, an employee who's passed a fit test but later finds the fit of the respirator unacceptable must be given a reasonable opportunity to select a new facepiece and be retested.
The employer is responsible for recording the results of fit testing. As stated under 29 CFR 1910.134(m)(2), the following information must be recorded: The name of the employee; the type of test performed (QLFT or QNFT); specific respirator tested; date of the test; and the results of the test. This information must be retained until the next fit test is administered.
Fit testing should not be confused with a respirator fit check. A fit check, or "user seal check" as it's referred to in appendix B to 29 CFR 1910.134, should be performed each time a tight-fitting respirator is donned to ensure there's an adequate seal. The appendix provides guidelines for performing positive- and negative-pressure fit checks but states, "User seal checks are not substitutes for QLFTs or QNFTs."
29 CFR 1910.134, Respiratory Protection Standard
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