Radiation Protection and Environment (Jan 2019)
Evaluation of protection factor of respiratory protective equipment using indigenously developed protection factor test facility
Abstract
Protection factor (PF) of a respirator is a number that describes the effectiveness of various classes of respirators in providing protection against exposure to airborne contaminants (including particulates, gases, vapors, and biological agents). The PF is derived from the ratio of the concentration of an airborne contaminant (e.g., hazardous substance) outside the respirator (Co) to the concentration inside the respirator (Ci) (i.e., Co/Ci). As the PF increases, there is an increase in the level of respiratory protection provided to employees by the respirator. PF Test Facility for the estimation of PF for various respiratory protective equipment was designed, fabricated, and installed at the Respiratory Protective Equipment Laboratory of Health Physics Division. The test facility consists of established air flow at a breathing rate through respirator darn on a human dummy and two identical tapings for iso-kinetic sampling from outside and inside the respirator. These tapings are coupled to two identical optical particle counters (OPCs) for the measurement of aerosol concentration simultaneously, and data acquired by the two OPCs are analyzed for estimating PF for different particle sizes using GRIM AEROSOL software. The results obtained from the studies carried out using this unique setup – air-purifying respirators such as half face mask, full face mask, and powered air-purifying respirators – were found offering a PF of 14, 112, and 1328, respectively, for selected range of 0.28–0.3-μm size standard sodium chloride (NaCl) aerosols. Standard NaCl aerosols used in experiments are polydispersed. However, the 0.3 μ size range (0.28–0.3) was selected as a benchmark for efficiency ratings and PF of respirators because it approximates the most difficult particle size for filters to capture and the least filtration efficiency is obtained in this range. This article brings out the details of design features of the setup and studies and results obtained for various types of respirators used in nuclear facilities.
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