If a respirator does not contain an exhalation valve, and the respirator wearer sneezes or coughs, one may expect previously collected particles to be reaerosolized.
This may be of special concern in environments contaminated with airborne microorganisms.
The percentages of reaerosolization were measured in a test setup where the number of reaerosolized particles were registered by dynamic aerosol size spectrometry relative to the number of previously collected particles or bacteria.
Experiments at low relative humidity have shown that the reaerosolization of particles below 1 mum, including Mycobacterium tuberculosis surrogate bacteria, does not exceed 0.025%, even if the re-entrainment air velocity is as high as 300 cm/sec (i.e., 37 times the air velocity through the respirator during breathing under heavy workload conditions).
The reaerosolization of larger particles into dry air was significant at the highest re-entrainment velocity of 300 cm/sec, which simulates violent sneezing or coughing : 0.1% for 3 mum and about 6% for 5-mum test particles.
No reaerosolization was detected at relative humidity levels exceeding 35% at these conditions.
Thus, it is concluded that the reaerosolization of particles and bacteria, collected on the fibrous filters of N95 respirators, is insignificant at conditions encountered in respirator wear.
Mots-clés Pascal : Exposition professionnelle, Protection personne, Protection individuelle, Masque protection, Respirateur, Microorganisme, Mycobacterium tuberculosis, Mycobacteriaceae, Mycobacteriales, Actinomycetes, Bactérie, Performance
Mots-clés Pascal anglais : Occupational exposure, Person protection, Individual safety equipment, Protective mask, Respirators, Microorganism, Mycobacterium tuberculosis, Mycobacteriaceae, Mycobacteriales, Actinomycetes, Bacteria, Performance
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 98-0104194
Code Inist : 001D16C06. Création : 22/06/1998.