A detailed investigation of N95 respirator sterilization with dry heat, hydrogen peroxide, and ionizing radiation

In the present ongoing pandemic, the N95 respirator is an essential protective barrier to suppress the spread of the SARS-Cov-2 virus and protect the frontline worker from exposure. The N95 respirators are meant for single usage; however, they can be used after sterilization, considering the economy and shortfall in availability. At this juncture, the performance of the respirator after various types of sterilization and usage condition is required to be analyzed in detail. With this motto, this work has proceeded. The respirator’s filtration efficiency (FE), breathing resistance, and quality factor are evaluated for two face velocities (5.8 ± 0.2 and 26.4 ± 0.9 cm/s). Sterilization techniques used here are dry air oven heating at 70–80 ± 3°C for 30 and 60 min, gamma irradiation for cumulative dose 15 and 25 kGy, and soaking in liquid hydrogen peroxide for 30 min. The filtration performance and electrostatic surface charge density are used to determine the facemask’s efficacy after sterilization. The respirator’s physical, chemical, and morphological degradation were investigated using materials area density, microscopic analyses, FTIR, Raman spectroscopy, EPR, and TGA analyses. The highest reduction in filtration efficiency is 29.36 ± 0.49–36.08 ± 1.78% after irradiation due to a reduction in the charge density (71–133%) of the respirator layers. However, the FE does not reduce significantly (0.39 ± 0.52 to −2.46 ± 0.60) for dry air heat and H ₂ O ₂ sterilization despite a change in charge density (0.4–53%), but there is no direct correlation with FE. Electrostatic charge measurement of the filtration layer is a crucial indicator of FE degradation. Hence, dry air heat and H ₂ O ₂ soaking are found to be the most suitable sterilization methods. No significant degradation was observed on the physical, chemical, and morphological properties of respirators layers after sterilization.