Can you trust an n95 mask that has followed the rules of decontamination?

Yes, we can trust because of the shortage of N95 masks. The shortage comes due to the high pandemic of COVID-19. As part of restricted reuse strategies, decontamination of N95 FFRs may be considered. Extended usage can also be used as part of restricted reuse techniques, whereby a N95 FFR is worn before being reused for several patient contacts and then preserved or decontaminated.

Researchers, including those from the University of California Los Angeles (UCLA) in the United States, have suggested that N95 respirators minimize exposure to airborne infectious agents, including the recent SARS-CoV-2 coronavirus, and are one of the main components of personal protective equipment used by clinical staff to prevent the spread of Covid-19.

The report, published in the journal Emerging Infectious Diseases, noted that attempts to find new decontamination methods that can expand their use have been motivated by critical shortages of these masks.

"While N95 respirators are intended for only one use before disposal, N95 respirators can be decontaminated and reused up to three times in times of shortage," said UCLA co-author James Lloyd-Smith of the report.

"But it is important to preserve the integrity of the fit and seal of the respirator," Lloyd-Smith added.

In the analysis, several decontamination methods were tested by scientists on small parts of the N95 filter fabric that were exposed to the virus, including the use of vaporized hydrogen peroxide, dry heat at 70 degrees Celsius, ultraviolet (UV) light and 70% ethanol spray.

All four methods removed the detectable viable virus from the N95 fabric test samples, according to the researchers.

To assess their reuse reliability, the scientists then treated completely intact, clean respirators using the same decontamination procedures, during which they volunteered to wear the masks for two hours to determine if they retained a proper fit and seal over the face.

They decontaminated each mask three times, using each one using the same method. Masks treated with vaporized hydrogen peroxide suffered no defects, according to the report, meaning they could theoretically be reused three times.

After three decontaminations, those treated with UV light and dry heat started to demonstrate fit and seal issues, the researchers said, suggesting that these respirators could theoretically be reused twice.

They concluded that vaporized hydrogen peroxide was the most successful approach because, after just 10 minutes of treatment, no signs of the virus could be found.

Based on the results, as long as the methods are implemented for at least 60 minutes, the scientists said UV light and dry heat are also suitable decontamination procedures.

However, after two sessions, the ethanol spray weakened the integrity of the respirator's fit and seal, and they do not recommend it for decontaminating N95 respirators.

According to the researchers, before any reuse, individuals decontaminating an N95 respirator should closely check the fit and seal over the face.

Decontamination Methods:

The following conditions should be fulfilled by a successful contamination technique:

The target organism, such as the SARS-CoV-2 virus that causes COVID-19, should be effective against it.

The filtration and electrostatic attraction of the respirator, which are essential to its proper operation and meet the strict specifications of filter efficiency and breathing resistance, should not be damaged.

It should have no effect on the fit of the respirator.

The individual wearing it should be healthy.


Fumigation is a procedure that decontaminates and enables the reuse of N95 masks. Present vaporized hydrogen peroxide procedures are used by Duke University Hospitals in Durham, North Carolina to decontaminate masks so they can be reused. The system uses advanced hydrogen peroxide vaporizing devices and a closed facility where the masks can be exposed to the vapor.

To kill viruses and germs without damaging the mask content, hydrogen peroxide permeates the layers of the mask. The decontamination process itself takes 20 minutes, but de-gassing normally takes 4 hours before it is safe to enter the decontamination room.

Heating in Hot Water:

This "regeneration treatment" for the reuse of N95 masks is planned specifically for household use and includes two steps:

Steep the used N95 mask in hot water for 30 minutes at a temperature of > 56 ° C (typically 60-80 ° C). Dry the mask for 10 min with a standard-but non-static-hair dryer.

This step is crucial for restoring the electrostatic charge that is vital to the filtering mechanism of the mask. Effective regeneration is confirmed by sprinkling tiny scraps of paper with the mask-the electrostatic charge has been restored if the paper sticks.


Another successful way of decontamination and reuse of N95 masks is the use of an autoclave that most hospitals and many clinics also typically have on hand to sterilize surgical equipment for the clinical setting. Steam sterilization at 121 ° C for 30 minutes is recognized by the US Centers for Disease Control and Prevention as the most commonly available and effective process for disinfection and sterilization in healthcare facilities.


A group experimented with baking at Stanford University. Their present standard is to bake N95 masks for 30 minutes at 75 ° C. Temperatures of 85 ° C or 100 ° C also seemed to work well in initial tests, but 125 ° C was too big. The output of the polypropylene starts deteriorating at that temperature.

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