An N95 respirator is a filtering facepiece that protects the wearer from airborne particles by filtering out at least 95% of very small particles. Unlike a loose-fitting surgical mask, the N95 must form a tight seal against the face to prevent contaminants from leaking around the edges. The effectiveness of the device depends entirely on the quality of this seal.
Since face shapes and sizes vary significantly, the seal is not guaranteed simply by donning the mask. Fit testing is the mandatory procedure designed to ensure that a specific make, model, and size of N95 respirator correctly seals to an individual’s face. This testing confirms the mask provides the anticipated level of protection before use in a hazardous environment.
The Purpose of Fit Testing
The purpose of N95 fit testing is the safety of the wearer, as an inadequate seal allows airborne contaminants to bypass the filter material. If the mask is incorrectly sized or shaped, the protective barrier is compromised, and the user can inhale harmful particles. This procedure confirms the selected respirator model is compatible with the wearer’s unique facial structure.
Fit testing is also a non-negotiable requirement for regulatory compliance in occupational settings. The Occupational Safety and Health Administration (OSHA) mandates this procedure in the United States under its Respiratory Protection Standard, 29 CFR 1910.134. This standard requires that any employee who must wear a tight-fitting respirator pass an appropriate fit test before using the device in the workplace. The test ensures the employer meets their legal obligation to provide properly fitted equipment. A successful fit test verifies the respirator has the potential to provide adequate protection, provided the user performs a seal check every time they put on the mask.
Methods of N95 Fit Testing
Respirator fit testing uses two methodologies: Qualitative Fit Testing (QLFT) and Quantitative Fit Testing (QNFT). Both methods require the wearer to execute a series of movements and exercises while wearing the chosen respirator to simulate typical work activities. The specific movements include:
- Normal breathing
- Deep breathing
- Turning the head side to side
- Nodding the head up and down
- Talking
Qualitative Fit Testing (QLFT)
QLFT is a subjective, pass/fail method relying on the wearer’s senses to detect a test agent. The individual wears the N95 under a hood while a harmless aerosol is introduced, typically saccharin (sweet taste) or Bitrex (bitter taste). If the wearer tastes the agent, the respirator seal is broken, and the test fails. This method is faster and less expensive, but it depends on the wearer’s accurate sensory response. OSHA accepts QLFT only for tight-fitting respirators that require a fit factor of 100 or less.
Quantitative Fit Testing (QNFT)
QNFT is an objective method that uses a specialized instrument to numerically measure the amount of leakage into the facepiece. Devices like the PortaCount connect to the respirator and measure the concentration of ambient particles both inside and outside the mask. The device calculates a “fit factor,” which is the ratio of the particle concentration outside the mask to the concentration inside the mask.
For a half-mask respirator like the N95, a minimum fit factor of 100 is required to pass the test. QNFT provides a precise, numerical score that removes subjective reporting. The exercises performed sometimes include a “grimace” test, where the subject intentionally challenges the face seal by smiling or frowning.
When Fit Testing is Required
N95 fit testing is tied to specific triggers to ensure the wearer is always protected by a proper seal. The first requirement is the initial fit test, which must be successfully completed before an employee uses a tight-fitting respirator for the first time in the workplace. This test must use the specific make, model, style, and size of the respirator the employee will wear for their assigned tasks.
Annual Fit Test
The annual fit test must be conducted at least once every 12 months, according to the OSHA standard. This yearly retesting is mandatory to confirm that the respirator still provides an acceptable seal despite small changes that occur over time. This regular assessment helps maintain the integrity of the respiratory protection program.
Triggering Events
A fit test must also be conducted whenever a triggering event occurs that could compromise the face seal. These events include switching to a different size, style, make, or model of respirator. Retesting is also necessary following changes to the wearer’s physical condition, such as significant weight gain or loss, facial scarring, major dental work, or cosmetic surgery.