ABSTRACT: The main goal of this study was to investigate multiple factors (faceseal leakage, combustion material, particle size, breathing flow rate, and breathing frequency) that affect the performance offered by negative pressure respiratory protection devices, including an elastomeric full facepiece, an elastomeric half-mask, an N95 filtering facepiece respirator (FFR), and a surgical mask.  Challenge aerosols included NaCl particles and combustion particles generated by burning different materials.  This research effort consists of three related studies. In study one, the effects of faceseal leakage and origin of challenge aerosol (combustion of wood, paper and plastic) on the performance of a full facepiece and a half-mask elastomeric respirator were tested. The study revealed that the origin of challenge aerosol significantly affects the particle penetration through unsealed and partially sealed half-mask.  Increasing leak size increased the total particle penetration.  In study two, the effect of particle size on the performance of an elastomeric half-mask respirator against combustion aerosols was examined. For the partially sealed and unsealed respirators, the penetration through the faceseal leakage reached maximum at particle sizes > 100 nm when challenged with plastic aerosol, whereas no clear peaks were observed for wood and paper aerosols. The particles aerosolized by burning plastic penetrated more readily than wood and paper. Study three was focused on the effect of breathing frequency on the total inward leakage (TIL) of an elastomeric half-mask respirator donned on an advanced manikin headform challenged with combustion aerosols. The frequency effect was less significant than flow rate. The greatest penetration occurred when respirators were challenged with plastic aerosol at 30 L/min and 30 breaths/min. Overall, the results presented in this dissertation provide an extensive database, which is useful for respirator manufacturers, regulatory agencies, respiratory protection researchers, and end-users operating in various occupational environments.

Nanoparticles