Abstract
A survey of the performance of expiratory valves used in air-purifying respirators is presented. Valves chosen for the study represented the four major valve design types in use in this country. Operating pressure, resistance to flow, and dynamic leakage were evaluated. The study of leakage included an investigation of the effects of valve orientation, covering, humidity, and work rate on dynamic leakage. Test results demonstrated significant differences in performance between valve types.
