Performance of air purifying organic vapor respirators in valveless, bidirectional flow configurations.
Coover SR; Reist PC; Hudgins PA
Am Ind Hyg Assoc J 1982 Aug; 43(8):622-625
Modifications to current valve design in air purifying organic vapor respirators were described which extended the service life of tested equipment from 1.5 to 3.6 times when used for carbon-tetrachloride (56235) and vinyl-chloride (75014). Current design required separate inhalation and exhalation valving to prohibit exhalation through the sorbent bed, which was thought to saturate it with water vapor, and rendering it useless. Tests of bidirectional flow through the sorbent bed of a new valveless long life air purifying respirator from the 3M Company showed that exhalation through the sorbent bed partially desorbed the contaminant and extended sorbent bed effectiveness. In comparisons of this respirator with a standard air purifying organic vapor respirator cartridge, both respirators exceeded the NIOSH certification requirement for organic vapor respirators (minimum 50 minute breakthrough time for carbon- tetrachloride when tested at 1000 parts per million and 64 liters per minute). Similar results were obtained when vinyl-chloride was the test contaminant. Both respirators showed marked reduction in air purifying capacity when used under conditions of continuous flow and lower contaminant concentration or alternating contaminant exposure. Dramatic increases in air purifying capacity were observed for both respirators under conditions simulating exhalation through the respirator cartridges. Aqueous saturation of sorbent by exhaled breath was not observed. The authors conclude that although bidirectional respirators may have extended service time due to contaminant desorption during exhalation, there is an increased resistance to exhalation in this configuration which may not be tolerable to some wearers.
NIOSH-Publication; NIOSH-Grant; Equipment-design; Air-quality; Air-purifying-respirators; Laboratory-testing; Respiratory-protection; Chemical-properties; Airway-resistance
American Industrial Hygiene Association Journal
Environmental Sciences & Engr Univ of North Carolina Sch of Public Health 201 H Chapel Hill, NC 27514