How to clean and reuse an N95 mask

You’re not supposed to reuse the common N95 filtering facepiece respirator mask. But given that they’re almost impossible to find (or impossible to afford) amid the coronavirus pandemic, here are some acceptable methods to decontaminate and reuse common N95 masks.

We’ve gathered advice from three credible sources: 

• N95 guidelines for healthcare professionals from the CDC
• A 2009 paper in the Annals of Occupational Hygiene
• An article by Dr. Peter Tsai, a designer of the modern N95 mask

Now playing: Boil, steam and bake: N95 masks are on the menu

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First, how not to clean your N95 mask

To maintain the effectiveness of the mask, never use these methods:

• Spraying or wetting with aerosol or liquid alcohol.
• Washing in soapy water.

Dr. Tsai indicates that these methods can break down the inherent electrostatic charge that is key to the way an N95 filters small particles. They can reduce a mask’s effectiveness by a third to a half.

How to clean your N95 mask

There are three cleaning methods, which experts find credible and you can do easily at home.

Method 1: Rotation

Dr. Tsai cites a study in the New England Journal of Medicine that uses a round robin rotation of masks so that each one is rested for at least 72 hours before being worn again. Tsai has not experimentally verified this method himself, but it relies on the widely held belief that the coronavirus should not survive more than 72 hours on an inhospitable host, like the surface of an N95 mask. The downside to this method is that you need four masks per wearer, and that’s assuming you use only a single mask each day. But if you just make a single trip for essentials any given day, the numbers work. 

Method 2: Steaming or boiling

Dr. Tsai says submerging an N95 in 125C/260F degree steam or boiling water for 3 minutes will disinfect the mask without significantly reducing its filtration efficiency (FE). Don’t excessively stir the mask if you boil it, use only enough manipulation to keep it submerged. If your mask has paper outer and inner layers, neither the steam or boiling methods are advisable as they will disintegrate those paper layers that hold the filter medium between them.

Method 3: Baking

I hesitate to include this method because, while simple, it assumes you have a second, dedicated oven for this purpose. If not, you run the risk of contaminating your main food preparation oven. Researchers at Michigan State University refined this method using a laboratory oven, and Dr. Tsai concurs that heating a mask for 30 minutes at 70C (160F) is an effective decontamination method.

The most important step

Don’t ruin your freshly decontaminated mask by handling it incorrectly. Don’t let your hands create a bridge between the particle-trapping front of the mask and the ostensibly clean back of it. Practice these CDC N95 steps to don and doff your mask properly. 

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While the CDC officially says there is no way to determine the number of times you can reuse a mask safely, these techniques from credible viral transmission experts create reasonable alternatives in this unprecedented time.