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Exhalation Valve Leakage of Scott Air Pak II Pressure Demand Facepiece Used by Melville N.Y. Fire Department.

NIOSH 1981 May:10 pages
The cause of exhalation valve leakage of a pressure demand face piece was investigated. The NIOSH Field Investigations Group was asked by a fire department to investigate problems experienced with the Scott Air Pak II, 30 minute pressure demand, self contained breathing apparatus. The problem was smoke leakage into the face piece during use in the demand mode. A face piece tightness test was performed on the face piece and a visual inspection was performed on the disassembled parts of the face piece and breathing tube. Results of the face piece tightness testing revealed that air leakage was occurring through the interior face piece exhalation valve. The visual inspection showed that the outer lip of the interior exhalation valve was pinched between the valve cavity and the valve assembly body, which caused the valve to deform and pull away from the valve seat. This condition was the cause of the valve leakage. This leakage could be stopped by switching the respirator to the pressure demand mode. Two other similar devices were tested and they did not have the pinched valve. The author concludes that during the use of the respirator in the pressure demand mode, the valve is not functional. The pinched valve will not compromise the performance of the respirator while in the pressure demand mode.
Breathing; Respiratory-protective-equipment; Safety-equipment; Industrial-hygiene; Inhalants; Breathing-atmospheres; Air-quality; Respiratory-equipment; Breathing-zone;
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Division of Safety Research, NIOSH, U.S. Department of Health, Education, and Welfare, Task No. 00736, 10 pages