Fit testing and user seal checks

A tight-fitting respirator protects only as well as it seals. Faces vary enormously in size and shape, and no single model fits everyone. Fit testing is how a program confirms that a specific make, model and size of respirator seals on a specific worker's face. User seal checks are the quick daily checks that the respirator is on correctly. This lesson explains both, along with the facial hair rules that cause so much friction in workplaces.

Why fit testing matters

Studies of workers wearing respirators without fit testing have repeatedly found that many achieve only a fraction of the expected protection, and some get almost none. A half mask with an APF of 10 that leaks badly may deliver a real protection factor of 2 or 3. Fit testing does two things. It screens out respirators that do not seal on a particular face, so the worker can be offered a different model or size. And it trains the worker in how a good fit feels, which improves how they put on the respirator every day.

When fit testing is required

OSHA requires fit testing of all tight-fitting respirators before an employee first uses the respirator, whenever a different facepiece (size, style, model or make) is used, and at least annually thereafter (1910.134(f)(2)). Additional fit testing is required when the employee, the PLHCP, a supervisor or the program administrator reports changes in the employee's physical condition that could affect fit, such as facial scarring, dental changes, cosmetic surgery or an obvious change in body weight (1910.134(f)(3)). If the employee finds the fit unacceptable, they must be given a reasonable opportunity to select a different respirator and be retested.

Fit testing applies only to tight-fitting facepieces. Loose-fitting hoods, helmets and visors do not need it. Fit testing must also be done with the same model and size the worker will use at work, and while wearing any other equipment that could affect fit, such as safety glasses, hearing protection or a hard hat.

Qualitative fit testing

A qualitative fit test (QLFT) is a pass or fail test that relies on the worker detecting a test agent by taste, smell or irritation. The worker first takes a sensitivity test without a respirator to confirm they can detect the agent. Then, wearing the respirator inside a hood or enclosure, they perform a series of exercises while the agent is introduced. If they detect the agent, the test fails.

Qualitative tests are simple and inexpensive but limited. Because the result depends on the worker's honest response and senses, they can only confirm a fit factor of about 100. They are therefore permitted only for respirators that need a fit factor of 100 or less, which in practice means half masks and filtering facepieces, and full facepieces only when they are used in atmospheres where a half mask would be sufficient.

Quantitative fit testing

A quantitative fit test (QNFT) measures how much leaks in. The most common method uses a condensation particle counter, such as a PortaCount, that counts tiny ambient particles outside and inside the facepiece through a probe or adapter. The ratio is the fit factor. Other methods generate a test aerosol, or use controlled negative pressure (CNP) to measure the leak rate when the facepiece is briefly sealed and air is drawn out.

Each exercise in the test produces its own fit factor. The overall fit factor is not the simple average but the harmonic mean, which gives more weight to the exercises where the fit was worst. This reflects how leakage actually adds up: a few seconds of poor fit let in far more contaminant than many minutes of good fit keep out.

The standard protocol uses exercises that simulate work movements: normal breathing, deep breathing, turning the head side to side, moving the head up and down, talking aloud, bending over and normal breathing again. A grimace exercise may be included to break and reset the seal but is not counted. Shorter protocols for certain respirator types have been validated and are accepted in both countries' practice.

OSHA's pass criteria for quantitative fit testing are an overall fit factor of at least 100 for tight-fitting half facepieces and at least 500 for tight-fitting full facepieces (1910.134(f)(7)). Appendix A of the standard sets out the accepted protocols, including several shortened protocols added in 2019 for condensation nuclei counter testing.

Conducting a good fit test

A fit test is also a training session. A good fit tester checks medical clearance first, confirms the worker has not eaten, smoked or chewed gum shortly before a taste test, offers several models and sizes, lets the worker choose the most comfortable respirator that seals, observes donning, and explains what was seen. CSA Z94.4-18 added a comfort assessment as part of fit testing, recognizing that a respirator that hurts after an hour will not be worn properly for a shift.

User seal checks

A user seal check is a quick test the wearer does every time a tight-fitting respirator is put on, to make sure it is seated properly. It is not a substitute for a fit test, but it catches twisted straps, displaced facepieces and damaged valves.

If a seal check fails, adjust the respirator and repeat. If it still fails, do not enter the contaminated area; report it so the respirator can be inspected or the worker refitted.

Facial hair and other interferences

Facial hair that lies under the sealing surface of a tight-fitting respirator breaks the seal. Research shows that even a day or two of stubble measurably reduces fit factors, and beards can reduce protection dramatically. That is why both countries require tight-fitting respirator users to be clean-shaven where the respirator seals. Moustaches and other facial hair that stay entirely inside the facepiece without touching the seal or interfering with valves may be acceptable.

OSHA prohibits tight-fitting respirators from being worn by employees who have facial hair that comes between the sealing surface and the face or interferes with valve function (1910.134(g)(1)(i)). Where facial hair is a religious practice, Title VII of the Civil Rights Act requires employers to accommodate unless doing so causes undue hardship, and since the Supreme Court's 2023 decision in Groff v. DeJoy undue hardship means substantial increased costs in relation to the business. The usual accommodation is a respirator that does not depend on a face seal, such as a loose-fitting PAPR or supplied-air hood, where it provides adequate protection.

Other interferences include spectacle temple bars passing under a full-facepiece seal, which is why full facepieces need special spectacle inserts; head coverings or hoods under the straps; jewelry; and dentures, whose removal can change face shape. Workers who wear corrective lenses, hearing protection or hard hats with respirators should be fit-tested wearing them.