title: Wearing an N95 respirator concurrently with a powered air-purifying respirator: effect on protection factor.
abstract: OBJECTIVE
  To determine if using an N95 filtering face-piece respirator concurrently with a loose-fitting powered air-purifying respirator (PAPR) offers additional protection to the wearer.
  
  
  METHODS
  We used a breathing mannequin programmed to deliver minute volumes of 25 L/min and 40 L/min. We measured the baseline protection factor of the PAPR with its motor operational and then deactivated (to simulate mechanical or battery failure). We tested 3 replicates of 3 different N95 models. We glued each N95 to the breathing mannequin and obtained a minimum protection factor of 100 at 25 L/min. We then placed the PAPR on the mannequin and took protection factor measurements with the N95-plus-PAPR combination, at 25 L/min and 40 L/min, with the PAPR operational and then deactivated.
  
  
  RESULTS
  The N95 significantly increased the PAPR's protection factor, even with the PAPR deactivated. The effect was multiplicative, not merely additive.
  
  
  CONCLUSIONS
  An N95 decreases the concentration of airborne particles inspired by the wearer of a PAPR.
authors.affiliation: National Personal Protective Technology Laboratory of National Institute for Occupational Safety and Health of Centers for Disease Control and Prevention, PO Box 18070, 626 Cochrans Mill Road, Pittsburgh, PA 15236, USA. dtn0@cdc.gov
authors.forename: Marc R
authors.initials: MR
authors.lastname: Roberge
authors.forename: Mark R
authors.initials: MR
authors.lastname: Vojtko
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Roberge
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Vojtko
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Landsittel
mesh_terms: D000328:Adult; D000391:Air Microbiology; D018562:Disease Transmission, Infectious / Q000517:prevention & control*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D019570:Inhalation Exposure / Q000517:prevention & control*; D008348:Manikins; D008954:Models, Biological; D012134:Respiratory Protective Devices