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This study was to test the filtration efficiency and breathing resistance of N95 respirators of different storage periods using the most penetrating particle size aerosol by automated filter tester (TSI, model 8130). quality factor (qf) was calculated to access possible effects of storage conditions and disinfection methods such as autoclaving and Gamma irradiation on the electric quality of fibres of the respirators.The analysis of N95 respirators with different storage conditions revealed that: A statistical difference (p=0.0453) was noted in aerosol filtration among N95 respirators of various storage periods, and the penetration was lower in respirators within the valid date compared with those expired respirators. There was also a statistical significance (p=0.0082) in breathing resistance among various storage periods. Autoclaving method of disinfection increased penetration, but decreased qf in respirators within valid dates when compared with those without disinfection. The dosage of 10 kGY, 25 kGY or 30 kGY Gamma irradiation also increased penetration, resistance and decreased qf. There was no significant difference on penetration, resistance and qf between respirators within or outside the valid dates when they were treated with the same disinfection methods except that after autoclave, respirators within valid date have significant lower breathing resistance compared with the expired respirators (p=0.0282).Although the various storage periods of N95 respirators reveal statistical significance, however, this is not the major affecting factor of filters fibre charge and filter quality. The method of Gamma irradiation appears stronger than storage period and autoclave method in affecting filters fibre charge and qf.