title: Pressure drop of filtering facepiece respirators: How low should we go?
abstract: BACKGROUND
  This study was undertaken to determine the mean peak filter resistance to airflow (Rfilter) encountered by subjects while wearing prototype filtering facepiece respirators (PRs) with low Rfilter during nasal and oral breathing at sedentary and low-moderate work rates.
  
  
  METHODS
  In-line pressure transducer measurements of mean Rfilteracross PRs with nominal Rfilter of 29.4 Pa, 58.8 Pa and 88.2 Pa (measured at 85 l/min constant airflow) were obtained during nasal and oral breathing at sedentary and low-moderate work rates for 10 subjects.
  
  
  RESULTS
  The mean Rfilter for the 29.4 PR was significantly lower than the other 2 PRs (p < 0.000), but there were no significant differences in mean Rfilter between the PRs with 58.8 and 88.2 Pa filter resistance (p > 0.05). The mean Rfilter was greater for oral versus nasal breathing and for exercise compared to sedentary activity (p < 0.001).
  
  
  CONCLUSIONS
  Mean oral and nasal Rfilter for all 3 PRs was at, or below, the minimal threshold level for detection of inspiratory resistance (the 58.8-74.5 Pa/l×s-1), which may account for the previously-reported lack of significant subjective or physiological differences when wearing PRs with these low Rfilter. Lowering filtering facepiece respirator Rfilter below 88.2 Pa (measured at 85 l/min constant airflow) may not result in additional subjective or physiological benefit to the wearer.
authors.affiliation: Centers for Disease Control and Prevention, Pittsburgh, Pennsylvania, United States of America (National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, Technology Research Branch).
authors.forename: Jung-Hyun
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Centers for Disease Control and Prevention, Pittsburgh, Pennsylvania, United States of America (National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, Technology Research Branch). dtn0@cdc.gov.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Roberge
authors.affiliation: Centers for Disease Control and Prevention, Pittsburgh, Pennsylvania, United States of America (National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, Technology Research Branch).
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Powell
authors.affiliation: Centers for Disease Control and Prevention, Pittsburgh, Pennsylvania, United States of America (National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, Technology Research Branch).
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Shaffer
authors.affiliation: 3M Company, St. Paul, Minnesota, United States of America (3M Personal Safety Division).
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Ylitalo
authors.affiliation: 3M Company, St. Paul, Minnesota, United States of America (3M Personal Safety Division).
authors.forename: John M
authors.initials: JM
authors.lastname: Sebastian
mesh_terms: D000328:Adult; D061808:Air Filters / Q000592:standards*; D000399:Air Pressure; D005260:Female; D006801:Humans; D008297:Male; D005082:Physical Exertion / Q000502:physiology; D012119:Respiration; D012134:Respiratory Protective Devices / Q000592:standards*; D012146:Rest / Q000502:physiology; D055815:Young Adult
keywords: filter; nasal breathing; oral breathing; respirator