Respiratory protective equipment (RPE) protects the wearer from inhaling hazardous airborne particles, gases, or vapors. This protection relies entirely on the respirator forming a tight, leak-free seal against the user’s face, forcing all inhaled air to pass through the filter media. Without an adequate seal, contaminants bypass the filtration material through gaps between the mask and the skin, rendering the protection ineffective. A fit test verifies that a specific model, style, and size of respirator can achieve this necessary facial seal for an individual user.
Defining the Fit Test Methods
The procedure used to verify the seal of a tight-fitting respirator falls into two main categories: qualitative or quantitative fit testing. Qualitative Fit Testing (QLFT) is a subjective, pass/fail method that relies on the wearer’s sensory perception. This test involves introducing a harmless, detectable challenge agent into a hood placed over the user’s head.
The challenge agents used are substances with a distinct taste or smell, such as saccharin (sweet), Bitrex (bitter), or isoamyl acetate (banana oil). If the wearer can taste or smell the agent during the test exercises, it indicates air is leaking past the respirator’s seal, resulting in failure. QLFT is generally used for half-mask respirators and disposable filtering facepiece respirators, but it does not provide a numerical measure of the fit.
Quantitative Fit Testing (QNFT) is an objective method that uses specialized instruments to measure the actual amount of leakage. This method does not rely on the wearer’s senses and can be used to test any tight-fitting respirator. The machine directly measures the concentration of particles both outside and inside the mask while the user performs a series of movements. The result is a numerical value known as the Fit Factor, which provides a precise measure of the seal’s integrity.
The Quantitative Fit Factor Metric
The Fit Factor is the numerical result of the quantitative fit test, representing the effectiveness of the respirator’s seal on an individual. It is calculated as a ratio of the particle concentration outside the mask to the concentration measured inside the mask. This calculation is expressed by the formula: Fit Factor equals the concentration outside divided by the concentration inside the facepiece.
The result is a dimensionless number indicating how many times cleaner the air is inside the respirator compared to the air surrounding it. For example, a Fit Factor of 100 means the particle concentration outside the respirator is 100 times greater than the concentration measured inside. A higher Fit Factor signifies a better seal and a greater reduction in contaminants reaching the wearer.
The testing instrument continuously calculates this ratio throughout the test exercises, which include movements like bending, talking, and turning the head side-to-side. These movements simulate the actions a worker performs on the job, challenging the mask’s seal under realistic conditions. The overall Fit Factor is usually an average or composite of the individual measurements recorded during these dynamic exercises.
Interpreting Passing Score Requirements
The passing range for a fit test is not a single, universal number but a minimum Fit Factor score determined by regulatory bodies based on the type of respirator worn. These minimum thresholds ensure the respirator provides an adequate level of protection to the user. The required score is directly correlated with the respirator’s Assigned Protection Factor (APF), which is the expected level of workplace protection.
For tight-fitting half-mask respirators, which cover the mouth and nose, the minimum passing Fit Factor required is 100. This threshold applies to both elastomeric half-masks and filtering facepiece respirators when tested quantitatively. Achieving a score of 100 or higher is required to pass the test.
Full facepiece respirators cover the entire face from the chin to the hairline and have a significantly higher passing requirement. For these devices, the minimum required Fit Factor is 500. This higher number reflects the expectation that a full facepiece, often used in higher-hazard environments, provides a greater degree of protection.
Practical Steps After a Failed Test
Receiving a failing Fit Factor score, whether numerical or based on subjective detection of the challenge agent, necessitates immediate action before the respirator can be used. The first step involves methodically troubleshooting the fit of the current respirator. The user should check the mask’s position, ensure the straps are adjusted to the proper tension, and verify that the nosepiece is correctly molded to the bridge of the nose.
After making adjustments, the individual must be retested with the same respirator to see if the fit has improved. If the respirator continues to fail, it indicates that the specific model or size is incompatible with the person’s facial structure. The next step requires trying a different size, brand, or model of respirator facepiece.
If a user consistently fails the fit test with multiple models, they may need to explore alternative respiratory protection options that do not rely on a tight facial seal. These alternatives include hood-style powered air-purifying respirators (PAPRs) or supplied-air respirators, which maintain positive pressure inside the hood to prevent leakage. For qualitative tests, a short waiting period is required after a failure to allow any lingering test agent to dissipate before a retest.