Know Your Respiratory Fit-Testing Protocols

July 30, 2024|Industrial Hygiene in the Workplace, Respiratory

Current respirator fit-testing protocols and the impact of OSHA’s modified 1910.134 standard on respiratory protection program implementation & resource allocation

By: Rob Brauch, Contributor

Fit-testing of tight-fitting respirators has been required to be part of a written respiratory protection program (RPP) under US DOL OSHA 1910.134 for decades. The standard covers both qualitative (QLFT) and quantitative (QNFT) methods and provides the details of each method’s specific fit-test requirements. Both methods are used to determine that the type, style and size of the respirator is correct for each individual worker included in the employer’s RPP.

All fit-test protocols are designed to replicate working conditions by having the test subject perform exercises, such as deep breathing, turning the head side-to-side, talking and others specified in the Appendix A section of 1910.134.

Qualitative fit-testing (QLFT) involves using a physical “challenge agent,” such as isoamyl nitrate (a.k.a., banana oil), saccharine or a bitter-tasting substance to be aerosolized and delivered manually using a nebulizer under a protective hood. This method relies solely on the expertise and dedication of the operator and the truthful, subjective response of the subject being tested. This method, while seemingly simple, is actually quite physically demanding and ergonomically stressful for the test operator, when done correctly, and can take up to 15 minutes to administer. It does not provide an objective measurement of fit, as does QNFT. (Note: OSHA does not allow QLFT for full-facepiece respirators and SCBAs, which must achieve a fit factor at least 10 times the Assigned Protection Factor (APF), or a minimum value of 500, which can only be done using the QNFT method.)

Quantitative Fit-Testing

Alternatively, quantitative fit-testing (QNFT) uses a dedicated fit-testing machine specifically designed to make objective measurements using either an Ambient Aerosol Condensation Nuclei Particle Counting (CNC) instrument or a Controlled Negative Pressure (CNP) device to test that the seal of the respirator fits the individual wearer under simulated work conditions. These include the test subject performing exercises to recreate movement that could cause a seal leak to occur in the course of daily activities.

These QNFT fit-testers use scientifically accurate means to detect whether a seal leak has occurred during the fit-testing procedure. Both types present an objective result, which is calculated and presented as the Fit Factor (FF).

The minimum numerical value needed to pass the fit-test will vary by respirator type—with a minimum of 100FF for half-facepiece and all-filtering facepieces (N95) and 500FF for full-facepiece respirators. (Note that these values are minimum values—and these can vary for those who fall under NFPA, CSA or ISO standards—or whose application calls for a higher protection factor based on level of hazard expected, such as CBNRE response missions.)

How The Tests Differ

The primary difference between the two measurement techniques (CNC and CNP) are that the CNP method can only be used on full-face and half-facepiece respirators, whereas the CNC method can test all types of respirators, including N95s. That’s because the CNC method is counting ambient particles as small as 2,500 nanometers mean diameter or less, sampled from the ambient air and from inside the respirator to determine the precise fit factor based on measured results.

Other differences include the way in which the test exercises are performed, with the CNC method making the calculation of the FF in real-time as the exercises are performed. The CNP method requires the user to “hold their breath” while the sensor in a CNP device measures pressure inside the mask to determine if a leak is occurring while the subject is stationary. If the test subject fails to hold their breath during the actual measurement, the device will alert the operator, and the test exercise must be repeated.

Fit-testing of tight-fitting respirators has been required to be part of a written respiratory protection program under US DOL OSHA 1910.134 for decades. The standard covers both qualitative and quantitative methods and provides the details of each method’s specific fit-test requirements. © Vasili – stock.adobe.com

Each method has its proponents, and all methods are capable of producing an OSHA-compliant result—but, at what cost? Qualitative testing can take up to around 20 minutes or more per subject to perform correctly, and this results in a high cost per test. And, it is still dependent on a subjective response, which may be very difficult for a test subject whose sense of smell and taste has been compromised by SARS-CoV2 and has resulted in long-term sensory loss.

Compliant quantitative fit-tests using a CNC device were originally developed with a Fit Test Protocol using a set of seven different subject exercises: normal breathing, deep breathing, turning head side-to-side, moving head up-and-down, talking, grimacing, bending over—and then repeat exercise one, normal breathing. This approach required around seven minutes to execute—less than half that of qualitative tests.

Compliant tests using the original CNP protocol required eight exercises to be performed. However, OSHA later modified this to a reduced set of exercises called the CNP redon fit test protocol that uses three subject exercises (facing forward, bending over and head shaking) and two “redon” exercises to remove and redon the respirator. This resulted in a test time closer to three minutes, if the user is able to hold their breath during each of the measurements needed to calculate the fit factor. Regardless, the CNP method is limited to only half- and full-facepiece respirators.

Approximately five years ago, OSHA issued a modification to Appendix A of Standard 1910.134 – Fit-Testing Procedures (Mandatory) specifically for inclusion of modified “streamlined” fit-test protocols for CNC fit-testing that reduced the number of exercises required for the two types of respirators (reusable half- and full-facepiece, and filtering facepiece/N95) to four. This means the total measurement time is now well below three minutes for testing any type of tight-fitting respirator. The exercises for the reusable respirators are bending over, jogging-in-place, head side-to-side and head up-and-down. For N95s, talking is substituted for jogging-in-place with the time to determine the fit factor values being the same.

As a result, the test times for performing compliant QLFTs have shifted in favor of objective measurements, and the productivity gains can be easily measured and quantified based on the wages being paid to the person performing the tests and the time differential between the QLFT and QNFT methods.

This, coupled with the dependency of qualitative tests on the human subjective response with no objective, science-based measurement to confirm the subjects’ conclusions, is a strong argument in favor of the quantitative method for delivering accuracy, consistency and repeatability of the pass/fail result. Moreover, the cost-savings alone will bring significant tangible benefits, as well as providing objective, machine-based evidence and record-keeping that is more in line with the expectations of practicing industrial hygienists.

Use the Right Tools

To put it simply, would you ask a worker if they “smell anything” in an H2S or Cl2 environment? Not likely, when personal gas monitors are plentiful and affordable. Or would you ask, “Does it seem loud to you in here,” when you can use an ANSI-compliant noise dosimeter? We have the right tools at our disposal to perform science-based, objective fit-test measurements with speed and accuracy that will more than offset the initial cost of obtaining a quantitative fit-test device. IHW