IRSST - Institut de recherche Robert-Sauvé en santé et en sécurité du travail

Efficacy of N95 Respirators in Conditions Representative of Human Breathing

  •   June 28, 2016

Montreal, June 28, 2016 – Researchers have tested the efficacy of N95 filtering face piece respirators in conditions of constant and cyclical air flow, simulating human breathing, from 42 to 360 L/min. N95 respirators are the personal safety equipment most commonly used in Quebec by industrial and health-care workers to protect themselves against exposure to ultrafine particles (UFPs).

The researchers first examined the impact of breathing frequency and inhalation flow rate on the efficacy of N95 respirators. They then compared the efficacy of N95 respirators in conditions of cyclical air flow with the results for constant air flow. Last, they assessed the impact of the clogging time of the filter on the performance of N95 respirators as a function of relative humidity and air flow (cyclical and constant).

“It is important to be able to determine the effectiveness of N95 respirators, because UFPs are potentially toxic and liable to cause serious health problems. They may be of natural origin (sea spray, smoke from forest fires or volcanic activity) or human origin (welding, diesel or exhaust fumes) and, due to their nanometric size, these particles may, once inhaled, be deposited deep in the lungs’ alveoli,” explained Ali Bahloul, a fluid mechanics expert at the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST).

The study results indicated that the influence of a high inhalation flow rate significantly affected the penetration of UFPs, while the impact of breathing frequency  was moderate. The researchers also established that with a constant air flow, the best assessment of UFP penetration levels is obtained using a moderate inhalation flow rate typical of the human respiratory cycle. The results also showed that filter clogging time and relative humidity have a major impact on particle penetration through N95 respirators.

The study is available for free download at To keep up with research at the IRSST, follow us on the Web, Twitter, Facebook, LinkedIn or YouTube.


Jacques Millette
Public Affairs Officer