Evaluation of Exhalation Resistance and Inspired Carbon Dioxide Concentration in Elastomeric Half-Mask Respirators with Modified or Covered Exhalation Valves

Though modifying or covering the exhalation valve of an elastomeric half-mask respirator (EHMR) may improve its potential efficacy for source control, it could also result in higher exhalation resistance or elevated concentrations of carbon dioxide gas (CO₂) in the respirator facepiece and subsequently increase user discomfort and reduce user acceptance. This study explores two approaches for modifying or covering the exhalation valves of EHMRs: (1) modifying EHMRs to filter the exhaled breath by removing the inhalation valve membranes and blocking the exhalation valve; (2) covering EHMR exhalation valves with surgical masks. NIOSH researchers evaluated the effects of these strategies on two measures of respirator performance—exhaled breathing resistance and inspired CO₂ levels—in nine EHMR configurations approved by the National Institute for Occupational Safety and Health.

Evaluation of Exhalation Resistance and Inspired Carbon Dioxide Concentration in Elastomeric Half-Mask Respirators with Modified or Covered Exhalation Valvespdf icon

Suggested Citation

NIOSH [2022]. Evaluation of exhalation resistance and inspired carbon dioxide concentration in elastomeric half-mask respirators with modified or covered exhalation valves. By Strickland KT, Fernando R, Schall J, Walbert G, Brannen J. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2022-109. https://doi.org/10.26616/NIOSHPUB2022109external icon