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What is Fit Testing?

What is Fit Testing?

Fit testing is the process to ensure that contaminated air cannot leak into a respirator and be inhaled. A respirator must form a good shield; even eyeglass frames, head coverings or beard, sideburns, subtle must not come between your respirator and your skin.

The U.S. Occupational Safety and Health Administration (OSHA) regulation 29 CFR 1910.134 and the Canadian Standards Association (CSA) standard Z94.4-11 require that all fit testing be performed in the negative pressure mode. Masks that are dedicated to a positive pressure respirator, such as a supplied air respirator or self-contained breathing apparatus that are only used in a positive pressure mode, must either be converted to negative pressure masks with the use of adapters, or negative pressure masks with the same sealing surface must be used as a surrogate.

CSA standard Z94.4-11 Section 9.1.7

Tight-fitting respirators shall be tested only in the negative-pressure mode regardless of the mode of operation in which the respirator is to be used. Note: This can be accomplished by temporarily converting the user’s face piece into negative-pressure mode or by using a surrogate negative-pressure air-purifying respirator with identical sealing surface.

When to do a Fit Test?

·Before you use your respirator the first time

·At least once a year

·If you experience physical changes, such as weight gain or loss or broken facial bones, that could affect the respirator’s fit

How do you do a fit test?

·Be clean shaven

·Put on your respirator as you would for your usual work conditions- for example, your straps should be as tight as they usually are when you are working

·Wear all the other equipment (such as glasses or goggles, hearing protection, and hard hat) you will have to wear when you are wearing your respirator.

·Seal check your respirator, using either a positive or negative pressure check.

·The tester will put a test agent that causes a taste, irritation, or smell into the air around the seal on your respirator (you may have to wear a special hood). Breathe in and report whether you can taste, feel, or smell the test agent. Instead, the tester may use special measuring instruments to determine whether there is any leakage into your mask.

·Sign the fit-test form to indicate that the test has been done.

Misconceptions of fit testing

One of the biggest misconceptions about fit testing is that it is not required for disposable respirators. This is untrue. Whether a worker is wearing a disposable or reusable respirator, all tight-fitting respirators must be tested per CSA Z94.4.

Another common misconception is that tight-fitting respirators attached to powered or supplied air systems don’t require fit testing. This is also untrue. Respirators used with powered and supplied air respiratory systems require fit testing in negative pressure mode so that they can be properly used in powered and supplied air mode.

Treen Safety conducts qualitative or quantitative fit testing for negative pressure respirators. Please contact us at 604-253-4588 or visit to learn more about Fit Testing or to book an appointment.


Fit Testing Your Respirator. (2009). [pdf] WorkSafe BC. Available at: [Accessed 29 Sep. 2017].

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