< Decontamination

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

Text updated on 2020-04-29

Several viruses, and most likely the SARS-CoV-2 coronavirus, are inactivated in a microwave oven for 20 seconds at 900-1250 W, provided water/moisture is available.

Currently, we do not have data on the effect of microwave ovens on the SARS-CoV-2 coronavirus. Observations on other viruses indicate that 20 seconds at 900-1250W in the presence of water generally inactivates viruses. Remember: water is essential.

How does it work? The microwave oven creates electromagnetic oscillations (microwaves) that penetrate the objects in the oven and rotates the water molecules in them. In the case of food, this agitation of the water molecules causes the food to heat up and eventually cook; in the case of a bowl of water, the water heats up and some of the water evaporates. Microwaves can inactivate pathogens in the presence of water but are ineffective on dry objects. Different types of viruses are inactivated after being placed in a microwave oven at 900-1250 W for 20 seconds.

The microwave oven is not recommended to decontaminate a mask. After 2 minutes in the microwave at 1250W in the presence of water, the amount of viral particles deposited on an FFR/FFP protective mask is reduced by more than 1000 times. However, the mask loses performance following such treatment: the elastic bands are damaged, the foam cushion in the nose area may come off, etc. To decontaminate an FFR/FFP mask, it is therefore preferable to put it in a conventional oven at 70°C (thermostat between 2 and 3) for 30 minutes, always in the presence of a bowl of water.

The distribution of microwave energy in the oven is not homogeneous and it is difficult to know whether the water vapour produced within the microwave oven will be distributed evenly. It is possible that decontamination will only take place on certain parts of the object. We, therefore, recommend an alternative decontamination method.

If you have no choice but to decontaminate an object in a microwave oven, first make sure it is free of metal and plastic. In the microwave oven, add a glass filled with water next to the object to be decontaminated in order to inactivate the virus. As always with microwave ovens, it is essential to add a glass or bowl of water if the object you want to heat does not contain water itself. The rotating plate is also important; if there is no turntable, remember that the microwaves are not evenly distributed, so move the object into the oven and start the microwave. To decontaminate, check that the entire object is accessible to the steam. If not, change the orientation of the object and restart the microwave.

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A microwave oven can inactivate HCV and AIDS viruses.

Siddharta, A., Pfaender, S., Malassa, A., Doerrbecker, J., Engelmann, M., Nugraha, B., ... & Goffinet, C. (2016). Inactivation of HCV and HIV by microwave: a novel approach for prevention of virus transmission among people who inject drugs. Scientific reports, 6(1), 1-10.

The avian coronavirus IBV and other viruses present in a liquid can be inactivated in 5 seconds in a 900 W microwave oven. The AIV avian influenza virus is inactivated in 20 seconds but not completely in 5 seconds.

G. Elhafi, C. J Naylor, C. E. Savage & R. C. Jones (2004) Microwave or autoclave treatments destroy the infectivity of infectious bronchitis virus and avian pneumovirus but allow detection by reverse transcriptase-polymerase chain reaction, Avian Pathology, 33:3, 303-306.

Microwaves can inactivate pathogens in the presence of water but are ineffective on dry objects.

Jeng, D. K., Kaczmarek, K. A., Woodworth, A. G., & Balasky, G. L. E. N. (1987). Mechanism of microwave sterilization in the dry state. Appl. approx. Microbiol, 53(9), 2133-2137.

Microwaves can inactivate pathogens in the presence of water but are ineffective on dry objects.

Vela, G. R., & Wu, J. F. (1979). Mechanism of lethal action of 2,450-MHz radiation on microorganisms. Appl. approx. Microbiol, 37(3), 550-553.

Effect of microwaving FFR masks.

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.

Effect of microwaving FFR masks.

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 adhesion on the face of FFR respirators is not affected after decontamination with microwaves (in the presence of water) or moist heat.

Bergman, M. S., Viscusi, D. J., Palmiero, A. J., Powell, J. B., & Shaffer, R. E. (2011). Impact of three cycles of decontamination treatments on filtering facepiece respirator fit. Journal of the International Society of Respiratory Protection, 28(1), 48.

Further reading

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

Can SARS-CoV-2 coronavirus be caught by eating?