Abstract
Current air purifying organic vapor design criteria require inhalation and exhalation valving to assure that exhalation does not occur through the sorbent bed. Testing of two brands of air purifying respirators in a bidirectional valveless configuration indicated that service lives for carbon tetrachloride and vinyl chloride could be extended by factors ranging from 1.5 to 3.6 as compared to conventional unidirectional valved configurations. Exhalation through the sorbent can partially desorb the contaminant without saturating the sorbent with water. These results suggest that it may be possible to extend the service lives of air purifying organic vapor respirators by deleting inhalation and exhalation valves. A disadvantage of a valveless configuration is extra breathing resistance encountered upon exhalation which may be intolerable to certain individuals.