A proper respirator fit is crucial for protecting workers from hazardous airborne particles. Fit testing verifies that a respirator fits snugly on the user’s face, providing the necessary protection.
There are two primary fit test methods: qualitative and quantitative. Understanding the differences between these methods is essential for selecting the right approach for your workplace.
Qualitative fit testing (QLFT) is a pass or fail test. It relies on the user’s senses to detect a test substance.
This method is effective for negative-pressure air-purifying respirators. It works best in places where the hazard level is below 10 times the permissible exposure limit (PEL). The test agents used in QLFT include:
Bitter Tasting: A solution with a bitter taste is sprayed into the air. If the user can taste the bitterness, the respirator fit is inadequate.
Sweet Taste: Like the bitter solution, a sweet-tasting aerosol determines if the respirator seal is effective.
Irritant Smoke: This test uses irritant smoke to provoke an involuntary cough if the respirator fit is compromised.
Sense of Smell: Some test agents rely on the user’s ability to smell them. If the user can smell the substance, it means the respirator doesn’t fit properly.
The qualitative test is straightforward and cost-effective, making it a popular choice for many workplaces. However, it is less precise than quantitative methods and may not be suitable for environments with higher exposure risks.
Quantitative fit testing (QNFT) uses instruments to measure how much air leaks around the face seal and gives a numerical result called a “fit factor.” This method works for any tight-fitting respirator and is more accurate than qualitative testing. This method works for any tight-fitting respirator and is more accurate than qualitative testing. The primary quantitative fit test methods include:
Condensation Nuclei Counting (CNC): This method counts the number of particles inside and outside the respirator. It calculates the fit factor by looking at the difference.
Controlled Negative Pressure (CNP): CNP technology checks for leaks by making a negative pressure inside the respirator. It measures how much air comes in.
Ambient Aerosol: This method uses particles in the air to check the fit factor. It compares particle amounts inside and outside the respirator.
Quantitative fit testing precisely measures respirator fit, making it ideal for environments with higher exposure risks.
Choosing the right fit test method depends on a few factors. These include the types of respirators used, the level of exposure risk, and any regulatory requirements.
The Respiratory Protection Standard 29 CFR 1910.134 mandates that fit tests be conducted before using a respirator in the workplace and at least annually thereafter. Both qualitative and quantitative fit testing methods are allowed under this standard. However, quantitative testing is recommended for high-risk environments because it is more precise.
The OHD AeroFit leverages Condensation Nuclei Counting (CNC) technology to provide accurate and reliable fit testing for N95 and elastomeric respirators.
The OHD QuantiFit2 utilizes Controlled Negative Pressure (CNP) technology to directly measure respirator leakage using air as the challenge agent.
Disclaimer: This article provides a general overview of the topic. It is not a substitute for the major requirements of OSHA’s Respiratory Protection Standard 29 CFR 1910.134.
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