Qualitative Versus Quantitative Respirator Fit Tests

Ever since the COVID-19 pandemic, more and more employees have become knowledgeable about and are wearing respiratory protection. According to OSHA 1910.134, employees who wear tight-fitting respirators must be fit tested. Tight fitting respirators include half- or full-facepiece or dust masks, SCBA, airline, or those with filter canisters. This is important, since only then can they reduce the exposure to the contaminant from which the respirator is designed to protect. This includes when the respirator is initially issued and when the user wears the respirator out in the field. Failure to ensure proper fit can make the respirator ineffective and give the wearer a false sense of security. Dust masks used on a voluntary basis are not required by OSHA to be fit-tested although many employers do test them as an added precaution for employees. There are two types of fit tests.

Qualitative fit testing uses the sense of taste or smell or reaction to an irritant to detect leakage into the respirator facepiece. It does not measure the actual amount of leakage. A hood is placed over the employee while wearing a respirator and an aerosol is sprayed into the hood. Whether the respirator passes or fails the test is based simply on the user detecting leakage of the test substance into the facepiece. There are four qualitative fit test methods accepted by OSHA which include isoamyl acetate, saccharin, bitter, and irritant smoke.

Qualitative fit test devices are inexpensive, can be conducted in the field, and allow the employee to use his/her own respirator(s). However, they can only be used to test air purifying half-face or full-face respirators with a fit factor of 100 or less. For example, a full-face air purifying respirator has an assigned fit factor of 50.The wearer must fully participate in the testing, and be sensitive to the sweet or bitter taste of the test aerosol. 

Quantitative fit testing uses a machine to measure the actual amount of leakage into the facepiece. The respirators used during this type of fit testing will have a probe attached to the facepiece that will be connected to the machine by a hose. There are three quantitative fit test methods accepted by OSHA which include generated aerosol, ambient aerosol, and controlled negative pressure.

Quantitative fit testing devices can be used on all types of tight-fitting respirators including dust masks, half-face and full face respirators, air-line respirators, and SCBA. They do not rely on sense of taste, smell, or irritation in order to detect leakage and do not rely on the employee to determine whether there is leakage. They are more expensive, are used in a fixed location, and use respirators that are equipped to attach to the test device.

Both types of respirator fit testing have their plusses and minuses. Whichever is chosen, it is important that they are conducted in conjunction with initial and follow-up training, medical monitoring, cleaning and maintenance, and supervision.

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