I’ve received many questions about mask usage since the CDC recommended the general public to wear masks. Masks are now required across the San Francisco Bay Area, and similar requirements are likely to trickle across the country, Using more masks means contaminating more masks, so we need to learn how to safely clean them. I was even interviewed by Romper on this topic, so let’s talk about it here. “Can I wash my N95 mask?” or “can I wash my surgical mask” boils down to two questions:
- Will the cleaning method disinfect the mask (both surfaces) from pathogens?
- Does the mask lose its integrity after cleaning? Will it still filter out pathogens? Will it still form a seal on my face and nose?
In my last post I discussed the risk-benefit ratio of mask usage, and why the general public should wear a mask. Now: Can I wash my N95 mask? What about my surgical mask?
Surgical vs N95 vs cloth masks
As I discussed in my last post, N95 masks are not believed to be superior against the majority of coronavirus spread (via droplets). Given the PPE shortage, officials recommend N95 and surgical masks to be reserved for hospital use. Cloth masks are recommended for the general public.
If frontline workers reuse contaminated N95 or surgical masks, they risk infecting themselves and spreading coronavirus to all their patients. So please donate masks to your local hospitals! You can use Mask Match to easily donate your masks.
All masks have shortcomings, and no mask is a substitute for physical distancing. Cloth masks may be effective in minimizing droplet spread but they are not complete barriers. But neither are other masks because our eyes are still exposed (one of the key virus infectious routes).
If you don’t already have a cloth mask, our surgeon general has a great demonstration of easily making one.
Can I wash my N95 mask?
If you have an N95 mask and are asking “can I wash my N95 mask?” the answer is simply “no”. N95 masks are typically disposable and simply not designed to withstand any decontamination without losing mask integrity.
So why is everyone researching how to decontaminate masks?
The PPE shortage is so severe, and frontline health workers are at such high risk, that hospitals are forced to reuse N95 masks.
So these decontamination methods are for hospitals, using hospital grade equipment. Not for individuals! None are perfect (vaporous hydrogen peroxide appears the most promising) and they include:
- Vaporous hydrogen peroxide
- Ultraviolet germicidal irradiation
- Moist heat
- Microwave steam treatment
- Liquid hydrogen peroxide
- Disinfectant wipes
I’ve explained the merits (with references) of each at the very, very bottom of the post for those who are interested.
What if I don’t have any other mask or cloth and I need to reuse my N95?
if an individual absolutely needs to reuse an N95 mask, some purely unofficial strategies are to:
- Prevent contamination in the first place. This is likely the safest approach, meaning you:
- Properly don/doff the mask.
- Wash hands before and after donning/doffing.
- Never touch the mask
- Never pull the mask below your chin or above your face.
- Additionally, you can wear a plastic face shield in front of the mask to prevent mask contamination from others talking, coughing, or sneezing near you. You can then easily wash the plastic face shield with less concern for the N95 mask being contaminated in the first place.
- Don’t try to wash your disposable N95 mask. Disinfectant wipes in particular are likely to reduce mask integrity. The same concern can be extrapolated to spraying or washing masks.
- “Rotating” masks has no supporting evidence, but it is unlikely to compromise the masks integrity. “Rotating” means leaving a mask aside after use (eg for several days) while using another mask, and another mask, then eventually using the previous mask again (maximizing the time between reusing the same mask). The theoretical idea is that allowing time between uses may result in virus death.
The CDC has the following recommendations to healthcare workers forced to reuse decontaminated masks:
- Wash hands before and after touching or adjusting N95 mask.
- Avoid touching the inside of the N95 mask.
- Use a pair of clean gloves when donning and performing a user seal check.
- Visually inspect the N95 mask to determine if its integrity has been compromised.
- Check that components (straps, nose bridge, nose foam) did not degrade. This can affect the quality of the fit and seal.
Can I wash my surgical mask?
There are many manufacturers of surgical masks and not every surgical mask has been evaluated. Based off the research from decontaminating N95 masks, it is likely that the same results hold for other masks. Conclusion: trying to wash disposable surgical masks is not recommended. The integrity is likely to be compromised from the above methods.
So if I can’t reuse N95 and surgical masks, what should I do?
Fortunately, we have a very simple and cost-effective solution: wear a cloth mask.
Since masks are generally more effective at reducing virus spread from sick people than protecting healthy people, a cloth mask is likely effective. Cloth masks are not perfect barriers but they can block droplets from leaving the mouth while talking, coughing, and sneezing – even if the cloth is damp.
Cloth masks can be laundered to decontaminate. Warm/hot water is recommended and a hot air drying cycle can be used after. While many other solutions have been discussed, I recommend this solution because:
- Everyone has access to laundry and soap and water.
- Laundry is cheap.
- This soap washing method minimizes anxiety. Relatively fool proof and reliable.
No UV light, no sun light, no microwaves, no hot steam. Just throw it in the laundry with detergent, warm/hot water, and a hot drying cycle.
- Local officials recommend N95 and surgical masks to be reserved for hospitals.
- The general public is recommended to use cloth masks whenever in public places. No mask provides a perfect barrier, but cloth masks appear to minimize viral spread with some effectiveness.
- Masks with “one way valves” do not optimally prevent COVID-19 spread. If used, these masks should be covered over with cloth.
- Disposable mask decontamination is being researched with hopes to allow masks to be reused. Importantly, a successful decontamination method must both kill pathogens and not compromise mask integrity.
- N95 mask decontamination is intended for hospitals that are unfortunately forced to decontaminate N95 masks for frontline workers to reuse. The methods are meant for hospital grade equipment with very particular specifications. These methods are not meant for home decontamination. Such methods include UV light, vaporized hydrogen peroxide, moist heat, steam, and ethanol, among others.
- While surgical mask decontamination is less formally studied, it is safe to draw the same conclusions about trying to decontaminate and reuse them. It should be avoided.
- Cloth masks can safely be cleaned with laundry. Hot water and drying are recommended.
- No type of face mask is a substitute for physical distancing!
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The information provided in this post in intended for general education. It is not medical advice. While I make every effort to provide the most up-to-date information, please note that new data is continuously becoming available and may change the conclusions I present here.
Hospital grade N95 mask decontamination methods
In hospitals, with hospital grade cleaning equipment, the following methods have been tried. I’ve tried to summarize results from multiple sources (below). You can see the primary sources for the decontamination specifications. Please note this research is constantly updating!
- Vaporous hydrogen peroxide: minimal mask integrity degradation but may not eliminate all virus. Appears most promising among all these flawed methods.
- Ethanol: mask integrity compromised but viral decontamination effective.
- Ultraviolet germicidal irradiation: significant mask degradation and may not eliminate all virus.
- Moist heat: significant mask degradation.
- Microwave steam treatment: variation in microwave heat distribution.
- Liquid hydrogen peroxide: promising but with limitations.
- Autoclaving: not recommended because of significant mask integrity compromise.
- Disinfectant wipes: not recommended because of significant mask integrity compromise.
Pre-publish: R. Fischer, et al. Assessment of N95 respirator decontamination and re-use for SARS-CoV-2
Pre-publish: Smith, et al. Effect of various decontamination procedures on disposable N95 mask integrity and SARS-CoV-2 infectivity
N95 decontamination research website (N95 decon)
CDC guidance on FFR (Filtering Facepiece Respirator, including N95) decontamination.