How Can we Disinfect and Reuse N95 masks–COVID-19

Personal protective equipment including masks are vital for protecting healthcare workers from infection with COVID-19.

But during this pandemic with masks in high demand by hospitals and individuals alike. It’s not surprising that many institutions are facing shortfalls. And are left scrambling to find alternatives.

There are two basic mask types commonly used in a clinical setting.

surgical masks are more loose fitting and generally provide good protection against larger droplets dispersed through coughs and sneezes.
In contrast, N95 respirators form a tight seal around the nose and mouth. Protect better against small aerosolized or airborne particles. And are therefore considered the best type of protection against SARS-COV-2.

So we’ll focus on this N95 mask for the remainder.

How to address the shortage of appropriate masks during a global pandemic?

Many regulatory bodies have guidelines. Which include allowing single use masks to be worn continuously throughout an entire shift known as extended use. Or allowing masks to be removed and put back on multiple times between patients within the same shift. This is known as reuse.Many institutions around the world are already requiring their staff to reuse their masks.

But what are the risks of reuse?

According to the CDC, the most significant risk of reuse and extended use is contact transmission. That is that the person might touch the surface of a contaminated respirator. And then infect themselves by touching their face.

How to Reduce the Contact Transmission?

One study found that nurses touch their face eyes or N95 respirator an average of 25 times per shift, during extended use.

In addition, respirators could also be contaminated with other common hospital pathogens. Such as mersa, or Clostridium difficile, which could also be transmitted through direct or indirect contact.

To reduce the risk of contact transmission. The CDC recommends using a cleanable face shield over an N95 respirator to avoid contamination. And discard that respirators if they’re obviously contaminated or damaged. Or they are hard to breathe through.

It is also vital that those who wear these masks wash their hands thoroughly before and after touching the respirator. We’ve even seen videos like this one pop up with interesting hacks. For avoiding contamination when donning and doffing a mask.

But even with these precautions, it’s still unclear whether the proper fit of the mask is compromised. From the wear and tear associated with reuse.

How to Safely wash or decontaminate N95 Masks while maintaining the mask ability

Since they are in short supply, is there a way to safely wash or decontaminate these masks between uses in order to extend the life of the available supply, and the decontamination process must not compromise the proper fit of the mask while maintaining the masks ability to filter out small particles like the virus in 2009.

Hydrogen Peroxide Vapor

A team at the National Institute of Occupational Safety and Health (also called NIOSH) showed. That a single treat and with hydrogen peroxide vapor UV irradiation. Or dry heat below 100 degrees Celsius did not affect the ability of N95 masks to filter small particles. Although they didn’t look at whether their treatment protocols were effective at decontaminating. Nor whether they affected the proper fit of the mask. This study paved the way for several more recent investigations.

A group at Duke University recently released a procedure for sterilizing N95 masks using hydrogen peroxide vapor. Their technique did not alter the fit of the mask. It left no residue other than water and it provided valid decontamination. Although they didn’t use Coronavirus, but instead tested using other biological indicators. Using this technique, they were able to repurpose 500 masks in one roughly four hour cycle. They also suggest that most masks could undergo this process at least 30 times without loss of fit.

Heating the Masks in an Oven

A team of researchers at Stanford University also examined several methods for disinfecting N95 masks. They started by heating the masks in an oven. The rationale for this is relatively simple. Several studies have shown that SARS -cov -2 begins to degrade at approximately 65 degrees Celsius. They chose a temperature of 75 degrees Celsius. Because of the wide availability of 75 degrees blanket warming ovens in hospitals. They found that heating at 75 degrees for 30 minutes did not compromise the function of the masks. Even when repeated for up to 20 cycles. This treatment was also sufficient to disinfect the masks although they used E.coli as a surrogate for Coronavirus. In their study, the team did not assess the effect on fit.

Well, this is a relatively simple procedure, they cautioned that we should not carry them out in a home oven.

UV Light

They also tested UV light. Previous studies have suggested that repeated exposure to UV light can lead to breakdown of the mask structures. But they found that 254 nanometers UV light for 30 minutes didn’t affect the filtering efficiency of the masks, even after up to 10 cycles.

However, the group cautioned that the limited penetration depth of UV light may affect the ability to disinfect particles deep inside the filter, so we need more research.

Notably alcohol and chlorine based disinfectants such as bleach interfered with the electrostatic charge on the masks. Which is an important component of the filter and significantly reduce their function. In addition, the masks retained bleach residue, which could prove harmful to the wearer. So while there are good options for sterilizing hard surfaces, we should not use them to clean N95 masks.

One last option that has been suggested but not well studied is to essentially do nothing and leave the masks to dry for several days.

This is based on the idea that viruses need moisture to remain viable. We don’t know how long starts code to remains viable in fabric. But it lasts 24 hours on cardboard, which is the closest material studied so far.

So leaving masks to dry for two to three days. Should conceivably be enough to render the virus no longer infectious.

However, it’s important to remember that this process won’t necessarily remove other contaminants. That could be present on the masks. And it would require that hospitals dedicate a relatively large, clean and uncontaminated space to the drying of masks.

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