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

Abstract

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 H2O2 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 H2O2 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.

Environmentally Sustainable Particulate Filter Fabricated via Induced Phase Separation of Bioderived Fungal Chitin and Poly(lactic acid)

“…The quality factors of PLA and ChPLA were lower than those of the PP web, but they were at comparable levels. In general, the quality factor of a layer of the MB web used for N95 grade face pieces ranges from 0.08 to 0.19 Pa –1 . , The filtration performances of bioderived filter webs, studied elsewhere, are compared in Table S2. ChPLA showed higher pressure drop and lower penetration than PLA regardless of the same base weight due to ChPLA’s lower porosity and smaller fibers that formed smaller open pores than the PLA web.…”

Influence of different treatment conditions on the filtration performance of conventional electret melt blown non-woven and novel nano FFP2 masks

“…However, one study has reported that filtration capabilities retained sufficient after IPA treatment with a filtration efficiency drop of only about 7–15%. The same study presented similar results after treatment with vaporized hydrogen peroxide (VHP) [ 18 ], which is another chemical normally known to lead to critical impairment of the filtration efficiencies of respirators as it is also the case with bleach or ethylene oxide (EO) [ 15 , 22 , 23 , 27 ].…”

“…On the other hand, the use of gamma radiation for physical sterilization was described to be rather critical for the filtration efficiency with reduced values around 70% [26,27]. However, chemical treatment with alcohols like ethanol [15,23] or IPA [22,23] are expected to diminish the filtration ability considerably due to a significant discharge of the electrostatically treated melt blown layer down to only a few percent of its original dipole charging value [18,22].…”

“…Focusing on autoclave sterilization, it is expected not to result in a significant reduction of filtration efficiency below 95% at a particle size of 0.3–0.5 μm as a previous study has shown investigating N95 certified mask types [ 17 ]. On the other hand, the use of gamma radiation for physical sterilization was described to be rather critical for the filtration efficiency with reduced values around 70% [ 26 , 27 ]. However, chemical treatment with alcohols like ethanol [ 15 , 23 ] or IPA [ 22 , 23 ] are expected to diminish the filtration ability considerably due to a significant discharge of the electrostatically treated melt blown layer down to only a few percent of its original dipole charging value [ 18 , 22 ].…”

Dry Heat as a Potential Decontamination Method on the Filtration Efficiency of Filtering Facepiece Respirators

“…To date, the disinfection methods of respirators mainly include dry heat [ 16 , 17 , 18 , 19 , 20 , 21 , 22 ], water vapor [ 16 , 17 , 23 , 24 , 25 ], chemical disinfectant [ 17 , 24 ], ultraviolet rays [ 16 , 17 , 18 , 23 , 24 , 26 ], hydrogen peroxide vapor [ 17 , 18 , 20 , 23 , 26 , 27 , 28 , 29 ], microwave radiation [ 17 , 18 , 19 ], supercritical CO 2 [ 29 ], high pressure steam [ 17 , 18 ], gamma radiations [ 30 , 31 ], and ethylene oxide [ 17 , 26 ]. However, limitations of these methods persist.…”