< Masks

Can a mask be reused?

Text updated on 2020-06-01

Effectively decontaminating your fabric mask or reusing your disposable mask is critical at this time. Although disposable masks are not designed to be reused, there are several effective decontamination methods that can be used without the mask losing its effectiveness!

We may have to reuse single-use non-washable masks in the face of a shortage, but also to limit waste. We must keep in mind that this type of mask can lose filtration efficiency and that we can become infected by decontaminating or reusing it because viral particles can remain trapped on it for 7 days. After each use, a mask must be considered contaminated!

Various mask decontamination methods were tested for the inactivation of viral particles but also for the effectiveness of the masks after treatment: use of solvents, UV exposure, dry heat, wet heat, microwaves. Most of these should be avoided as they rapidly degrade the effectiveness of the mask.

Fabric mask: wash it in the machine (preferably at 60°C) or by hand with soap. There is little risk of contamination because most of the virus does not survive 2 days on cloth, and heat or soap (but not all detergents) during washing inactivates the virus. In addition, if the mask has been exposed to coronavirus or if you are a person at risk, you can iron it. If your mask has a filter-type part (e.g., paper), discard it after each use.

FFR (face-piece respirator): place the FFR respirator at 70°C for 1 hour. Masks should remain effective for up to 20 cycles.

If the FFR respirator has had little exposure to the virus, has no metal parts (fire hazard), and you are not a person at risk, an alternative is to microwave the mask for 3 minutes at 1100 W (restored), placing it on a large bowl filled with 60 cL of water. You can rest it on chopsticks, using elastics placed across it, or using a net stretched by an elastic band. The straps of the mask should also be above the bowl. No part of the mask should touch the water. The mask should retain its effectiveness for up to 3 microwaving cycles without deformation or loss of filtration.

Surgical mask: if the mask has had little exposure to the virus and you are not a person at risk, you can use the envelope method. After 7 days, most of the virus is inactivated on a surgical mask. It is therefore possible to buy 7 masks, place the mask in a dated paper envelope after use, then let it rest for at least 7 days in the heat of the sun or a heater. Before using the envelope method, read the question COVID : Can a surgical mask be used more than once? An alternative is to put the mask in the oven at 70°C for 1 hour.

We advise to decontaminate in the oven or washing machine several masks at the same time to minimize energy use. Finally, always check that the mask is not damaged before putting it back on. Keep in mind that it is possible that small doses of viruses may be sufficient to cause contamination.

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Decontamination of N95 masks at 85°C, 60-85% humidity.

Anderegg, L., Meisenhelder, C., Ngooi, C. O., Liao, L., Xiao, W., Chu, S., ... & Doyle, J. M. (2020). A Scalable Method of Applying Heat and Humidity for Decontamination of N95 Respirators During the COVID-19 Crisis. medRxiv.

Comparison of the effectiveness of N95 surgical gauze ("gauze masks") and non-woven ("spunlace masks") masks after decontamination using dry heat (rice cooker), wet heat (autoclave), bleach, isopropanol, or ethanol.

Lin, T. H., Chen, C. C., Huang, S. H., Kuo, C. W., Lai, C. Y., & Lin, W. Y. (2017). Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: Effects of five decontamination methods. PloS one, 12(10).

Placing a respirator on a plastic container with holes on the top and water in the bottom, and leaving it in the microwave for 2 min at 1250 W deactivates more than 99.99% of the H1N1 virus.

Heimbuch, B. K., Wallace, W. H., Kinney, K., Lumley, A. E., Wu, C. Y., Woo, M. H., & Wander, J. D. (2011). A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets. American journal of infection control, 39(1), e1-e9.

A 30 minute treatment at 75°C maintains the filtering properties of N95 masks.

Liao, L., Xiao, W., Zhao, M., Yu, X., Wang, H., Wang, Q., Chu, S., & Cui, Y. (2020). Can N95 Respirators Be Reused after Disinfection? How Many Times?. ACS nano, acsnano.0c03597. Advance online publication.

After 7 days, 99.9% of the virus is inactivated on a surgical mask.  99.9% of the virus does not survive 2 days on tissues. Soap inactivates 99.999% of the virus in 15 min at 22°C.

Chin, A., Chu, J., Perera, M., Hui, K., Yen, H. L., Chan, M., ... & Poon, L. (2020). Stability of SARS-CoV-2 in different environmental conditions. The Lancet Microbe.

Comparison of physical deformation and filtration capacity after 3 decontamination cycles using several methods.

Bergman, M. S., Viscusi, D. J., Heimbuch, B. K., Wander, J. D., Sambol, A. R., & Shaffer, R. E. (2010). Evaluation of multiple (3-cycle) decontamination processing for filtering facepiece respirators. Journal of Engineered Fibers and Fabrics, 5(4).

Comparison of the decontamination of FFP respirators, surgical masks, or fabric masks after treatment in a rice cooker (100°C), with or without water.

Li, D. F., Cadnum, J. L., Redmond, S. N., Jones, L. D., & Donskey, C. J. (2020). It's Not the Heat, It's the Humidity: Effectiveness of a Rice Cooker-Steamer for Decontamination of Cloth and Surgical Face Masks and N95 Respirators. American Journal of Infection Control.

A review of the literature indicates that no treatment for 1 hour in the oven at

Gertsman, S., Agarwal, A., O'Hearn, K., Webster, R., Tsampalieros, A., Barrowman, N., ... & Gibson, J. (2020). Microwave-and Heat-Based Decontamination of N95 Filtering Facepiece Respirators (FFR): A Systematic Review.

Method for 99.9999% decontamination of FFPs respirators for 3 min on top of a water container at 1100 W in a microwave oven.

Zulauf, K. E., Green, A. B., Ba, A. N. N., Jagdish, T., Reif, D., Seeley, R., ... & Kirby, J. E. (2020). Microwave-Generated Steam Decontamination of N95 Respirators Utilizing Universally Accessible Materials. medRxiv.

After 1 hour at 70°C in the oven, 99.999% of the SARS-CoV-2 coronavirus on an N95 mask is inactivated. The fit factor decreases after 3 cycles but remains above 100, which is typically considered a good fit.

Fischer, R., Morris, D. H., van Doremalen, N., Sarchette, S., Matson, J., Bushmaker, T., ... & Judson, S. (2020). Assessment of N95 respirator decontamination and re-use for SARS-CoV-2. medRxiv.

Dry heat at 80°C for one hour does not significantly decrease the filtration capacity, breathability, elasticity of the straps, and the shape of FFR respirators, even after 20 cycles.

Viscusi, D. J., King, W. P., & Shaffer, R. E. (2007). Effect of Decontamination on the Filtration Efficiency of Two Filtering Facepiece Respirator Models. Journal of the International Society for Respiratory Protection, 2493.

The temperature must be precisely controlled during decontamination: Respirators left for 1 hour in the oven at 100°C have melted or have seen their filtration capacity drop below 95%. On the other hand, none of the 9 models tested melted or reduced their filtration capacity below 95% at 80 or 90°C.

Viscusi, D. J., Bergman, M. S., Eimer, B. C., & Shaffer, R. E. (2009). Evaluation of five decontamination methods for filtering facepiece respirators. Annals of occupational hygiene, 53(8), 815-827.

The different types of detergent do not inactivate the influenza virus with the same effectiveness or mechanism: potassium oleate (C18:1) is the most effective, sodium dodecyl sulphate (SDS) and sodium laureth sulphate (LES) are less effective, especially at low concentrations.

Kawahara, T., Akiba, I., Sakou, M., Sakaguchi, T., & Taniguchi, H. (2018). Inactivation of human and avian influenza viruses by potassium oleate of natural soap component through exothermic interaction. PloS one, 13(9).

Further reading

COVID: Can a surgical mask be used more than once?

Is the SARS-CoV-2 coronavirus resistant to cold or heat?

Can the SARS-CoV-2 coronavirus be inactivated in a microwave oven?

How long is the coronavirus infectious?

What are the different types of masks?

Why is it recommended not to wear a surgical mask for more than 4 hours?

Can a mask be used after its expiration date?

Is there any point in wearing a transparent face shield?