Development of a Particle Counting Method for Assessing the Biological Protection Factor of Respirators

摘要

This investigation developed and validated a highly sensitive method based on particle counting technology for assessing the protection afforded by chemical, biological, radiological, and nuclear respirators against biological threat agents. Inert monodisperse and polydisperse aerosols, representative in size to biological agents, were used to challenge a respirator fitted to a headform or worn by a human test participant. An aerosol spectrometer was used to measure aerosol penetration into the facepiece of the respirator. To demonstrate the method, monodisperse test aerosols and controlled mask leaks were used to generate an array of simulated protection factors (SPF) on the headform test apparatus. Human test participants were challenged with a polydisperse aerosol, which allowed for the measurement of several size specific protection factor (PF) values from a single test. Each test participant wore at least one expertly fitted respirator and several respirators with induced leaks in the peripheral seal to generate a wide range of PF measurements. A test to determine the effect of human generated background particles within the respirator was also conducted. In general, SPF and PF values were found to increase as the challenge aerosol particle size increased. Although subject generated in-mask background particles were found to limit the maximum measurable PF, the particle counting method sensitivity was sufficient to measure PF values up to 100,000.