QUALITATIVE VS. QUANTITATIVE FIT TESTING
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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.
Advantages of qualitative fit testing:
Low cost for kit and supplies.
Multiple employees can be simultaneously tested.
Simple pass/fail results.
Disadvantages of qualitative fit testing:
Chance of employee deception or inability to taste/smell solution.
Limited protection-factor verification (maximum fit factor of 100).
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.
Advantages of quantitative fit testing:
No protection-factor limit.
Documentation of numerical results.
No chance of employee deception or inability to taste/smell solution.
Disadvantages of quantitative fit testing:
Only one employee can be tested at a time.
More costly than qualitative fit testing.
Often times adaptors and different quantitative equipment is needed depending on the respirator model/type.