Due to the lack of N95 mask supplies, sanitize N95 masks is necessary in order to it is enable reused. The coronavirus disease pandemic 2019 (COVID-19) has caused a limited number of personal protective equipment, including the N95 respirator mask.

How to Clean and Reuse N95 Mask
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Wearing N95 has been recommended for medical personnel who carry out actions that are at risk of causing aerosols in COVID-19 patients. Based on the National Institute of Occupational Safety and Health (NIOSH) by the Centers for Disease Control and Prevention (CDC), wearing N95 has a filtration efficacy of at least 95% for aerosol sodium chloride, which has a size of 0.3 micrometers.

Decontamination of Viruses in N95 Masks

SARS–CoV-2 contaminates on the outer surface of the face masks than on the inner surface. On the outer mask surface, The SARS-CoV-2  life span is estimated to be around 72 hours, and the virus generally becomes inactive and does not penetrate to the inner surface.

How to Clean and Reuse N95 Mask?

How to kill the virus quickly is by irradiating, fumigating, steaming, heating, or roasting. according to the National Institutes of Health, the researchers have confirmed that there are several methods for decontaminating N95 masks in order to reusable.

Several methods of how to clean N95 masks (such as Vaporized hydrogen peroxide, ultraviolet light irradiation, dry and wet heating) have proven to be quite effective in decontaminating N95 respirators from the SARS-CoV-2 virus.

1. Vaporized Hydrogen Peroxide
Vaporized hydrogen peroxide sterilization is a method of decontamination using hydrogen peroxide at low temperatures. The Kenney PA et al. study examined the efficacy of Hydrogen Peroxide Vapor sterilization of N95 respirators for reusable. Based on this study, after five sterilization cycles, they found that masks to be the same as the initial condition without deformity.

A pilot study by The Dutch National Institute for Public Health and the Environment (RIVM) examined the sterilization of FFP2 masks, which resemble N95 masks, using the Vaporized hydrogen peroxide method. The results show that FFP2 masks can be used three times after being sterilized twice with hydrogen peroxide.

The study from Bergman et al. also found that between N95 masks with and without sterilization use Vaporized hydrogen peroxide method, there were no significant differences, and both had almost the same average penetration rates, which were below 4.01%.

2. Ultraviolet 
Ultraviolet light has been proven to be an effective method of killing microorganisms, but radiation from ultraviolet can degrade polymers to reduce the efficacy of N95 respirators. The Lindsley WG et al. study examined the sterilization of N95 respirators using the ultraviolet irradiation method at a dose of 120-950 J / cm2. Study results showed that this method is effective in the decontamination of N95 masks, but ultraviolet exposure can increase particle penetration in small amounts.

The Mills et al. study also showed that sterilization by ultraviolet irradiation could significantly reduce virus viability (> 3 log) in N95 respirators. Also, Heimbuch et al. demonstrated the efficacy of the ultraviolet irradiation method. In their study, ultraviolet irradiation> 1J / cm2 can eliminate viruses in N95 masks, and 20 cycles of radiations had no significant effect on compatibility, resistance airflow, or particles.

3. Dry heat
The dry heating method with a temperature of 70 degrees C for 30 minutes is one method that can kill the virus on the N95 respirator mask. Fischer et al.'s study showed that N95 masks could be sterilized by two cycles of dry heating. A recent study from Liao L et al. stated that dry heat with a temperature of 75 degrees C could be carried out as many as 20 cycles without damaging the N95 mask.

4. Wet heat
Mask sterilization by heating at a temperature of 60-70 degrees C with a relative humidity level of 80-85% is found effective in killing the flu virus. The Anderegg L et al. study tried to examine the effect of a sterilized N95 mask with a heat level of 85 degrees C for 30 minutes with a relative humidity level of 60-85%. The results indicated that after five wet heating cycles, there was no significant difference in the filtration efficacy of the new N95 mask with those that had been sterilized.

The study of Bergman et al. also found that performing wet heating sterilization at 60 degrees C with 80% to N95 respirators relative humidity has a good level of aerosol penetration filtering.

Comparison of the Efficacy of the Sanitary Mask N95 Methods

Fischer RJ et al. have compared four N95 mask decontamination methods for reuse, namely ultraviolet irradiation (260-285 nm), 70 degrees C dry heating, 70% ethanol, and Vaporized hydrogen peroxide.

This study found that the Vaporized hydrogen peroxide method had the fastest time to inactivate SARS-CoV-2 in the N95 mask. Ultraviolet light and 70 degrees C dry heating could inactivate SARS-CoV-2 at almost the same time but slower than the Vaporized hydrogen peroxide method.

As for the ethanol causes a loss of N95 integrity, so this method is not recommended. The study also stated that the N95 respirators decontamination using ultraviolet and Vaporized hydrogen peroxide could be done up to 3 times. But, the dry heat method can only be done up to two times.

Another study by Viscusi DJ et al. had compared the filtration efficiency of respirator masks in 10 decontamination processes. The results indicated that Vaporized hydrogen peroxide and ultraviolet irradiation are the decontamination methods that least changes the penetration of particles in respirator masks.

Reprocessing Recommendation N95
Based on the CDC recommendations, the wearing of respirator masks as personal protective equipment, including N95, is not recommended for routine decontamination. But in a crisis, reuse and decontamination of N95 masks can be done if needed. The N95 mask decontamination methods recommended by the CDC are ultraviolet irradiation, evaporated hydrogen peroxide, and wet heat.

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