AEROSOL PENETRATION BEHAVIOR OF RESPIRATOR VALVES

Exhalation and inhalation valves from half-facepiece negative pressure respirators were evaluated for leakage during an 8-hour cyclic breath ing test period using two work rates (415 and 622 kg-m/min) and two pa rticle sizes (0.3 and 0.8 mu m). Three different models (manufacturers ) of exhalation valves were tested, with two lots for each model. Exha lation valve leakage ranged from 0.0 to 0.03%; no failure of exhalatio n valves occurred. No differences in lot or manufacturer were found. D ifferences in particle size did not lead to differences in penetration at the lower work rate; at the higher work rate 0.3-mu m particles we re less penetrating than 0.8-mu m particles (0.03 versus 0.06%). When tested for air leakage at a pressure of 2.54 cm H2O, following the Nat ional Institute for Occupational Safety and Health certification metho d, exhalation valves exhibited no leakage either before or after the e xperiments. Inhalation valves averaged 20% leakage for all experiments ; 0.3-mu m particles were again less penetrating (13%) than 0.8-mu m p articles (27%). No inhalation valve failure occurred. No differences i n lot (within manufacturer) were found; there were, however, significa nt differences in particle penetration among the three manufacturers' inhalation valves. Airflow leakage through the inhalation valves did n ot change during the experimental period, but differed among the three manufacturers. Measurements using airflow leakage and particle penetr ation produced the same ranking for the th ree manufacturers' in halat ion valves.