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Respirator performance as a function of inhalation valve efficacy.

Campbell-DL; Allender-JR; Myers-WR
J Int Soc Respir Prot 1990; 8(1):26-32
The effect of inhalation valve efficacy on full facepiece respirator performance was assessed. Two models of full facepiece respirators without nose cups were modified by replacing the standard one way inhalation valves with one way valves that eliminated backflow during exhalation. The respirators were evaluated using a headform and breathing machine with the inhalation valve functional and with the valve partially defeated to allow backflow during exhalation. Acetone vapor was used as the challenge agent. The three concentrations determined experimentally included the pulmonary concentration, the exhalation valve or exhaust concentration, and the calculated concentration. Defeating the function of the inhalation valves significantly decreased the provided protection against the vapor challenge. The authors conclude that backflow through the inhalation valve during exhalation appears to result in the temporary trapping of contaminant both in the volume of the inlet passage and on the inner surface of the sorbent bed. Respirator manufacturers should therefore look toward the inhalation valve as a possible way to increase the protection provided by their respirators.
Personal-protective-equipment; Respiratory-protection; Safety-equipment; Health-protection; Protective-equipment; Industrial-safety; Equipment-design; Respiratory-protective-equipment; Analytical-models
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Journal of the International Society for Respiratory Protection