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What is the difference between qualitative and quantitative fit testing?

What's the difference between qualitative and quantitative fit testing?

Which method is objectively better?

There are two different methods of respirator fit testing: quantitative (QNFT) and qualitative (QLFT). But, what is the difference between the two, and which is better? 

Qualitative fit testing is a subjective pass/fail test method. It does not measure the leakage into or out of a respirator facepiece in a numerical way. (OSHA, 2012) This method relies on a person’s senses. If a user’s sense of smell or taste is compromised, or if the test is conducted improperly, there is a risk of a false fail or false pass.

Quantitative fit testers, such as PortaCount ® Respirator Fit Testers, objectively measure how effective a respirator fit is. PortaCount instruments use the Ambient Aerosol Condensation Nuclei Counter (CNC) Quantitative Fit Testing Method. Ambient Aerosol CNC-based quantitative respirator fit testing is not dependent on the wearer’s sense of smell or taste like qualitative respirator fit testing (QLFT). Instead, quantitative fit testers count particles inside and outside a mask worn by a test subject. It uses this data to calculate the fit factor, which is a strong indicator of how tightly the respirator is sealed to the wearer's face.

Why is a tight seal important?

What is the difference between qualitative and quantitative fit testing?A tight seal between a respirator and its wearer is shown to reduce inhalation of airborne, breathable hazards, including droplets or aerosols that could carry microbes or viruses. A properly fitted N95 that is worn correctly can block at least 95% of small airborne particles, including those found in aerosols and droplets. “The virus that causes COVID-19 is thought to spread mainly through respiratory droplets” from an infected person. (CDC, Aug 2020

Additional resources

For more information on COVID-19 visit the Center for Disease and Control Prevention FAQ page: https://www.cdc.gov/coronavirus/2019-ncov/faq.html

For more information on Respirator Fit Testers visit: 

For more information on Quantitative vs Qualitative Fit Testing visit:

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