Qualitative vs. Quantitative Respirator Fit Testing: A Technical History

Inhalation hazards are among the most common physical, chemical, and biological exposure risks for firefighters, industrial workers, and medical staff. The consequences of poor respirator fit can lead to injury, illness, disease, and even death.

The long search for better, safer, respirator fit tests

For more than a century, experts looked for ways to identify respirator leaks. They developed and refined a number of test methods, some of which (qualitative fit testing) relied on the olfactory senses and the subjective input of each respirator wearer. Eventually in 1974 and later in 1998, the United States Occupational Health and Safety Administration (US OSHA) became involved in selecting for use the methods of Qualitative (QLFT) and Quantitative (QNFT) respirator fit testing that would become the standard for protecting workers.

How quantitative respirator fit testing became the standard

If you’re interested in the story of how one method came out on top, read “Why Quantitative Respirator Fit Testing Beats Qualitative,” a paper by TSI’s experts in occupational health and safety and industrial hygiene. 

This 3-page paper describes QLFT and QNFT respirator fit testing methods in detail, shows how OSHA came to its position on QNFT, and explains why it’s more reliable and less subjective than other methods. Readers will gain a clear understanding of essential concepts like “fit factor,” “Permissible Exposure Limit,” and “Maximum Use Concentration,” and learn how they’re defined and calculated. Today, Ambient Aerosol CNC-based quantitative respirator fit testing is the preferred method for objective, reliable respirator fit measurement. 

If you’re an Industrial Hygienist, Occupational/Environmental Health & Safety professional, or Program/Fit Test Administrator whom is responsible for respiratory protection programs, you will find this paper to be essential reading.