Respiratory protection

Responding is Jeffrey Birkner, vice president, technical services and quality assurance for Moldex-Metric Inc., Culver City, CA.

Fit tests ensure a respirator is properly fitted to an individual. According to OSHA 29CFR 1910.134(f), fit tests must be performed at least once a year, or more often if required by a substance specific standard. There are two basic types of fit tests – qualitative and quantitative.

The tests most commonly used have been scientifically validated to be good tests to evaluate the adequacy of respirator fit.

Qualitative fit test kits are not prohibitively expensive (usually $100-$200) and can be easily performed in the field, but are based only on a subjective response provided by the person being tested. Quantitative fit test equipment is much more expensive (usually $4,000-$10,000), can be used in most but not all field environments, and provides an indication of respirator fit that does not rely on subjective responses.

A qualitative fit test is a pass/fail test that relies on the subject’s sensory response to detect the challenge agent. A challenge agent will cause the test subject to taste, smell or feel (through irritation) whether the challenge agent has penetrated the seal of the respirator. The most commonly used and scientifically validated qualitative fit tests are saccharin, Bitrex and Isoamyl Acetate (Banana Oil) tests. Saccharin (which is extremely sweet) or Bitrex (which is extremely bitter) is sprayed at the user wearing the respirator under a hood, which acts as a small test chamber.

A specific protocol is followed, but if the subject tastes the challenge agent (either saccharin or Bitrex) the respirator fit is deemed inadequate. This test can be performed only with respirators having a particulate filter. In fit tests with isoamyl acetate, the agent is allowed to evaporate into a hood containing the user wearing a respirator. If the subject smells the challenge agent (which smells like bananas), the respirator fit is deemed inadequate. This test can only be performed with respirators having an organic vapor chemical cartridge. In all three cases, if the challenge goes undetected after various exercises, the fit of the respirator is deemed adequate.

When performed properly, all three tests ensure the wearer has a fit factor of at least 100, which provides a tenfold safety factor and therefore allows the wearer to use the respirator with an assigned protection factor (APF) of 10. These qualitative fit tests have been validated for use with half-mask respirators, but may be used for full facepiece respirators. When performed on a full facepiece respirator, you may not assume an APF of greater than 10 because these qualitative fit tests have not been scientifically validated for numbers greater than this.

Quantitative fit tests use an instrument to measure the challenge agent inside and outside the respirator. It does not rely on any response from the test subject and provides an actual fit factor. The most commonly used fit test apparatuses are the Portacount and the Quantafit. They are portable and can be easily used by a program administrator for a respiratory program. When doing a quantitative fit test, the fit factor must equal a 100 for half-mask respirators and 500 for full-face respirators, which provides a safety factor of 10 – giving the half-mask and full-face respirators APFs of 10 and 50, respectively.

It must be stated again that these fit tests, whether qualitative or quantitative, must be performed on each wearer at least once a year to make sure the actual model and size respirator used by a particular individual achieves the minimal required fit factor. It is true that the actual protection that an individual gets when using his or her respirator in the field will vary, but many of the field studies performed seem to indicate that a minimal fit factor of 10 is a reasonable estimate for half-masks.

Editor's note: This article represents the independent views of the author and should not be construed as a National Safety Council endorsement.