As winter blows in to the Northern Hemisphere, coronavirus cases are on the rise. Unfortunately, this rise is once again putting N95 respirators in short supply at medical centers, nursing homes, and other facilities. The need to conserve PPE has led many to question whether these masks can be cleaned and reused in some way.

Even individuals outside of these high-risk environments, who wear surgical or cloth masks to prevent the spread of COVID-19, may question whether reusing their masks would be beneficial. Do you need to use a new mask every time you enter a different store? Can you rewear the same mask for several days in a row before washing it? And how can masks be cleaned effectively between wears?

Surgical and Cloth Masks

Surgical masks (the blue-and-white three-ply ones you see all over) are called disposable masks for a reason: they are meant to be disposed of after each day’s use and cannot be washed or reused. If you’re wearing one periodically over the course of a day (e.g., running errands), you don’t need to change it between errands, but you should throw it in a paper bag to keep it clean in the meantime.

The same would hold true for cloth masks, which should be washed daily. Shockingly, a study in the UK found that just 13% of those who wear cloth masks are maintaining them correctly, with many people changing them infrequently or washing them insufficiently between wears.

Virus particles can easily linger on a mask, especially when the mask has been donned and doffed several times, lain on surfaces that may be contaminated, or cleaned insufficiently. In addition, health experts say that a wet or soiled face mask leads to restricted airflow and minimized filtering of viral particles.

So how should cloth masks be washed? The easiest way is to throw them into your washing machine, with the temperature setting on at least 140 degrees Fahrenheit (60 degrees Celsius), and then tumble dry them on the hottest setting. These hot temperatures, combined with regular detergent, should kill any viral particles on the mask.

Don’t have a washing machine? You can also clean masks by hand by scrubbing both sides of the mask thoroughly with soap and very hot water for at least 20 seconds. Alternatively, you could soak them in a mild chlorine solution for 30 minutes and then rinse them with water and detergent. If you don’t have a dryer, you can air dry your mask by laying it on a flat, clean surface or hanging it by the straps in direct sunlight. (Some studies show that UVB rays in sunlight can kill COVID particles.)

In either case, inspect your mask before rewearing for any tears or stains, and ensure that it fits correctly.


N95 masks

In medical settings, many prefer N95 masks over the typical surgical masks. That’s because they have a better seal and use electrostatically charged fibers that repel virus particles from getting in or out.

(As an aside, not all N95 masks are created equal. The ones with a valve make breathing in and out easier, but they are also probably less effective in preventing the transmission of Covid particles.)

Like surgical masks, N95 masks are intended to be discarded after a single use. Because they are in such short supply, however, medical organizations like the CDC and WHO have been willing to take a more relaxed stance.

Their recent stance is that N95 respirators can be decontaminated and reused up to three times – but this is only if the respirator’s fit and seal are still effectively maintained.

N95 masks cannot be decontaminated with the basic washing protocol that cleans cloth masks. This is because part of the effectiveness of an N95 mask is that it carries an electrostatic charge. Washing the mask in water eliminates this charge, which negatively affects the filtering ability of the mask.

The use of dry heat produced by rice cookers, multicookers, ovens, and microwaves is one commonly touted method for cleaning these masks. Keep in mind, however, that using these appliances may cause the mask to become melted, damaged, or even set on fire if the mask is too close to the heating surface. 

For microwaving, which can be done at home, some studies suggest that 30 seconds is sufficient to decontaminate a mask. Dry heat, however, will take much longer to sterilize a mask, but the lengthy time in a high-heat environment can cause the mask to degrade.

Other options for N95 decontamination, such as UVGI and VHP, can be more effective, even though they can generally only be used in a laboratory setting. UVGI, or ultraviolet germicidal irradiation, is a disinfection method in which short-wave UV  light is used to inactivate the genetic material inside the virus, leaving it unable to infect a host or perform other functions. Current research suggests that UVGI can be extremely efficacious in N95 mask decontamination. Although the UV-C bulbs used for UVGI are not readily available, some currently-closed university research facilities may have these bulbs available in storage.

The use of VHP, or vaporized hydrogen peroxide, seems to be even more effective than UVGI, according to one study. VHP is a sterilization method commonly used to decontaminate reusable medical devices. While both dry heat and UVGI require at least a 60-minute decontamination process in order to be considered effective, vaporized hydrogen peroxide kills the virus in just 10 minutes, and appears to be extremely effective.

Remember that any of these processes are only recommended for a maximum of three times, and only if the fit and seal of the respirator are maintained.

Many people do not disinfect their masks correctly, and many healthcare facilities are overusing their N95 or inadequately cleaning them between uses. While the industry is working to match the production of N95 masks to the demand, and while sales of cloth masks continue to skyrocket, knowing how to effectively disinfect both types of mask is crucial to containing the virus.

Written by Robert Brown