Respiratory Protection Fit Testing

Fit Testing

3M Center for Respiratory Protection

Overview of the Fit Testing Process

Tight-fitting respirators must seal to the wearer’s face in order to provide expected protection. This includes disposable respirators (also called “filtering facepieces”). Therefore, fit testing is required in the US by the Occupational Safety and Health Administration (OSHA) before a user wears a mandatory respirator on the job, and must be assessed at least annually. In addition, fit tests should be performed:

  • Whenever a different size, style, model or make of respirator is used.
  • When any facial changes occur that could affect fit, such as significant weight fluctuation or dental work.

OSHA doesn’t require fit test administrators to be certified, just to know how to conduct a test, recognize invalid tests, and properly clean and maintain equipment. Read more about OSHA fit testing protocols.

There are two kinds of tests: qualitative and quantitative.

  • Qualitative Fit Test (QLFT)

    A qualitative fit test (QLFT) may only be used to fit-test:

    • Negative-pressure, air-purifying respirators, as long as they’ll only be used in atmospheres where the hazard is at less than 10 times the permissible exposure limit (PEL).
    • Tight fitting facepieces used with powered and atmosphere-supplying respirators.

    QLFT is pass/fail and relies on the user’s senses using one of four OSHA-accepted test agents:

    • Isoamyl acetate (banana smell); only for testing respirators with organic vapor cartridges.
    • Saccharin (sweet taste); can test respirators with a particulate filter of any class.
    • Bitrex® (bitter taste); can also test respirators with particulate filters of any class.
    • Irritant smoke (involuntary cough reflex); only for testing respirators with level 100 particulate filters.

    Each QLFT method uses seven exercises performed for 1 minute each:

    • Normal breathing.
    • Deep breathing.
    • Moving head side to side.
    • Moving head up and down.
    • Bending over (or jogging in place if fit test unit doesn’t permit bending at the waist).
    • Talking.
    • Normal breathing again.

    Read more about OSHA fit testing protocols.

  • Quantitative Fit Test (QNFT)

    A quantitative fit test (QNFT) can be used to fit-test any tight-fitting respirator. It involves using an instrument to measure leakage around the face seal and produces a numerical result called a “fit factor.” There are three OSHA-accepted QNFT test protocols:

    • Generated aerosol uses a non-hazardous aerosol such as corn oil generated in a test chamber.
    • Condensation nuclei counter (CNC) uses ambient aerosol and doesn’t require a test chamber.
    • Controlled negative pressure (CNP) uses a test that creates a vacuum by temporarily cutting off air. (There is also a fourth method, which is an abbreviated version of this one.)

    QNFTs use the same seven exercises as QLFTs, plus an additional “grimace” test where the subject smiles or frowns for 15 seconds.

    A fit factor of at least 100 is required for half-mask respirators and a minimum fit factor of 500 for a full facepiece negative-pressure respirator. 

The Importance of Fit

Respirator fit is important because it involves several major issues:

  • Seal.
  • Compatibility.
  • Stability.
  • Mask Man

    The Respirator's Seal

    A good fit means the respirator will seal to your skin. A respirator can only work when air passes through the filter. Air will take the path of least resistance, so if the seal isn’t there, the air will go around rather than through the respirator – and therefore lessen the protection.

  • User Seal Check: An Essential Everyday Test

    Employees wearing tight-fitting respiratory protection should perform a seal check each time they put on their respirator, and are required to do so by OSHA regulations unless the use is voluntary. A fit test ensures that the respirator is able to fit and provide a secure seal, but a user seal check ensures that it’s being worn right each time.

    Users can either perform a positive-pressure or negative-pressure seal check:

    • A positive-pressure check means blocking the exhalation valve on a half or full facepiece respirator or covering the respirator surface on a filtering facepiece, usually by using your hands, and trying to breathe out. If slight pressure builds up, that means air isn’t leaking around the edges of the respirator.
    • A negative-pressure check involves blocking the intake valves on a half or full facepiece respirator or covering the respirator surface on a filtering facepiece, typically using your hands and trying to breathe in. If no air enters, the seal is tight.

    See the product User Instructions for more details.

  • Compatibility with other PPE

    Safety glasses, hearing protection, face shields, hard hats and coveralls can all vie with a respirator for real estate on a person’s face, head or body. For instance, if a half face respirator doesn’t fit well (especially if it’s too large), it can overlap with glasses. The more that happens, the more fogging can potentially occur on glasses, and the more likely it is that they’ll interfere with the respirator’s seal.

    To catch these problems before they happen on the job, OSHA requires any PPE that could interfere with the respirator’s seal to be worn during the fit test.

  • Respirator Stability

    The better a respirator fits, the more stable it’s likely to be on the wearer’s face. Fit testing determines the respirator’s ability to retain its seal when the worker is in motion. That’s why test subjects are told to go through several exercises as part of testing. A respirator that shifts during movement may not be able to retain its seal.

Fit Hero Video


Fast Facts About Fit Testing

Fit testing is not only required by the U.S. Occupational Safety and Health Administration (OSHA); it’s vital to respiratory safety. This list provides some of the whys and hows of fit testing.

Fit Test Record


  • Fit Test Record

    The Fit Testing Record is the employer documentation that fit testing has been completed and passed for employees. This record must be kept with the respiratory protection program documentation until the next required fit testing.

Fit Test Wallet Card


  • Wallet Card

    A Fit Testing Wallet Card is documentation designed to be used by the employee to keep record of their fit test. Fit test results are not tied to the employer, so employees can transfer their valid fit test to another job as long as the same make and model respirator are available.

See the next step in your journey to optimizing your respiratory protection program.