Facepiece respirators are widely used to reduce the human exposure with biological warfare or emerging diseases are primarily within the range of 30 run to 3 µm. Due to the threat of bioterrorism, the need to evaluate the performance of existing health-care masks and NIOSH certified N95 respirators and the demand to improve their efficiency have significantly grown. We have developed and built a sophisticated laboratory facility for evaluating various respiratory devices with bioaerosol particles and their surrogates using a manikin based protocol in a 25 m3 indoor chamber. The aerosol concentrations are measured real-time inside and outside the mask worn by a manikin. The measurements are conducted by a particle size selective aerosol spectrometer. The penetration efficiency is determined as a ratio of these concentrations for specific particle size fractions at different breathing flow rates. The data obtained with biological particles and their non-biological surrogates showed the limitations of existing respirators for reducing inhalation exposure to airborne spores and virions. We developed a novel concept for enhancing the collection efficiency of conventional filtering masks. The emission of unipolar electric ions in the vicinity of the mask was found to decrease the particle penetration through the filter by one to two orders of magnitude. Given that the infectious dose of many agents is· in order of 101 to 103 particles, the ion emission effect should make a crucial difference with respect to the exposure and health risk.
UNIVERSITY OF CINCINNATI U. S. ENVIRONMENTAL PROTECTION AGENCY VETERANS AFFAIRS (VA) MEDICAL CENTER
Sergey A. Grinshpun and Tiina Reponen
DEPARTMENT OF ENVIRONMENTAL HEALTH, UNIVERSITY OF CINCINNATI, CINCINNATI, OHIO, U.S.A.