A research team from IRSST, a nonprofit scientific research organization in Quebec, Canada, has tested the efficacy of N95 filtering facepiece respirators in conditions of cyclical airflow, simulating human breathing. The study was focused on N95 respirators’ ability to protect industrial and healthcare workers against exposure to ultrafine particles, or particulate matter of less than 100 nanometers (nm) in diameter. Researchers examined the effects of breathing frequency and inhalation flow rate on the efficacy of N95 respirators, compared the results for the efficacy of N95 respirators in conditions of cyclical airflow with those for constant airflow, and studied the impact of the clogging time of the filter on the performance of N95 respirators as a function of relative humidity and both cyclical and constant airflow.

“The study results indicated that the influence of a high inhalation flow rate significantly affected the penetration of [ultrafine particles], while the impact of breathing frequency was moderate,” IRSST’s news release reads. “The researchers also established that with a constant airflow, the best assessment of [ultrafine particle] penetration levels is obtained using a moderate inhalation flow rate typical of the human respiratory cycle.” 

IRSST’s results also showed that filter clogging time and relative humidity have a “major impact” on particle penetration through N95 respirators. 

The full research report is available as a download from IRSST’s .