Performance Evaluationon Of Two N95 Filtering-facepiece Respiratorson Decomposition Products Of Sulfur Hexafluoride

Background: Respiratory protective device is designed to protect people from airborne pollutants. We generally evaluated the performance of respirator by testing its filtration efficiency, Fit Factor(FF), Total inward leakage(TIL) and etc.. Sulfur hexafluoride(SF6) is an important industrial raw material, which has stable physical and chemical properties. Due to its good performances of insulation and arc suppression, SF6 was widely used in electrical equipment. In the presence of an electric arc, corona or spark, SF6 will decompose into many chemically active products like acid gases and particles, which lead to severe lung injury when inhaled by workers.Objective: To assess the Fit factors of two N95 filtering-facepiece respirators(FFRs) and their filtration efficiencies for the decomposed products of sulfur hexafluoride(SF6).Methods: Two types of N95 FFRs(the particulate and the acid-proof respirators) were selected in this study. The fit factors and decomposed products of SF6, including particles, hydrogen fluoride(HF) and sulfur dioxide(SO2), were measured under experimental condition by TSI Porta Count Plus, fluorine ion-selective electrodes and spectrophotometer separately. The filtration efficiency was then calculated and compared.Results: The filtration efficiency of particles for both two models of N95 respirators were larger than 95%, and the highest inhalation resistance for both two models of N95 respirators were less than 350 Pa under airflow ranged from 10 to 95 L/min. When exposed to different concentrations of HF(low: 0-1.99 mg/m3, middle: 2-3.99 mg/m3, high: > 4 mg/m3), the acid-proof N95 respirator was more effective than the particulate respirator(P<0.05). The filtration efficiencies of acid-proof N95 respirator were 98.83%, 99.08%, and 99.03% from the lowest to the highest concentrations of HF, respectively. While the filtration efficiencies were 48.44%, 45.71%, and 47.31% for the particulate respirator. For four SO2 concentration ranges(0-2.49mg/m3, 2.50-4.99mg/m3, 5.00-9.99mg/m3, and >10.00mg/m3), the acid-proof respirator showed a high filtration efficiency within exposure to 1.5 hours:95.73%, 98.67%, 98.14%, and 97.78%, respectively; when exposure duration extended to 4 hours, the filtration efficiency of the acid-proof respirator decreased to91.97%, 82.28%, 70.12%, and 58.56%, respectively.Conclusion: The acid-proof N95 FFRs showed a better fit character than particulate N95 FFRs. Both the particulate and the acid-proof N95 FFRs met national standards on the particulate filtration efficiency and inhalation resistance. The acid-proof N95 respirator demonstrated to be more effective in filtering HF and SO2 than the particulate respirator. The filtration efficiency could decrease to an unsafe condition under longer exposure duration, timely replacement of respirator is recommended at the workplace.