Killing Corona; The Nuclear option

Can Microwaving my Mask Disinfect it from Viruses?

We’ve had hundreds of people ask us how to wash their masks. We’ve shown in previous articles that washing masks with water isn’t great. Now a new question has been thrown our way:

“Can I put my mask in the microwave to disinfect it?”

Let’s break this question down into 2 questions:

1. Can microwaving items disinfect them from viruses?

First, let’s take a look at whether household microwaves can actually kill (or ‘inactivate’) viruses. To date, there’s little research on microwaving masks. However, researchers in Germany analysed whether microwaving syringes and cigarette filters could work to reduce infectivity of Hepatitis C and HIV for drug users.

They took the plastic part of syringes and cigarette filters, then contaminated them with Hepatitis C or HIV. They then subjected them to 3 minutes in the microwave, at different power levels.

The results showed that microwaving at 360W for 3 minutes was enough to significantly reduce the virus infectivity.

To be on the safe side, these researchers recommended microwaving at 600 W, for 2 minutes or longer. The good news is, most household microwaves on high can reach up to 600W.

In the experimental conditions applied here, microwave irradiation for at least 2 min or longer at not less than 600 W is sufficient to reach a critical temperature which facilitates inactivation of HCV as well as HIV-1 or HCV/HIV-1.

But that’s for HIV and Hepatitis C, what about coronaviruses?

Well spotted! The researchers in Germany tested the effects of microwaving on Hepatitis C and HIV viruses, not coronaviruses. To date, there’s little research on microwaving Covid-19.

However research on human parainfluenza – an RNA virus just like Covid-19 – has been done.

These scientists from the Department of Microbiology at Oklahoma State University concluded that running a microwave on high for 3 minutes was enough to disinfect plastic petri dishes.

2. OK, but can I microwave a mask and will it affect its performance?

With the knowledge above, we now know that microwaving can kill or inactivate viruses. The next question is whether or not microwaving masks affect their filtration efficiency? To test this, we took a used 3M N95 mask, and commandeered the microwave in the kitchen.

Before microwaving the mask, we had to remove all the metal clips and nose strap from the mask.

This isn’t ideal. After removing the metal bits from the mask, the N95 mask became pretty much unusable. If your mask contains metal parts, then you may well end up having to destroy it before it even gets into the microwave.

There are some masks that don’t contain any metal parts, especially many of the DIY and handmade masks that are being used right now. we decided to continue with test for these cases. we took the 3M N95 mask and put it in the microwave on high for 3minutes.

After about 2 minutes, the microwave started smelling. It’s possible that leaving the microwave on for too long could damage it. However, not wanting to give up, we persevered!

After 3 minutes in the microwave and then waiting for the mask to cool down, we took a Met One GT521, and tested how well the mask was able to capture 0.3 micron particles –typically the most difficult size to capture. This is the same method we used to test the effectiveness of paper towel for making DIY masks.

Comparing effectiveness before and after microwaving, the data shows that microwaving the mask didn’t reduce the mask’s filtration effectiveness.

Wondering why microwaving can kill viruses?

The scientists from Germany explained how a temperature of 56–60 °C is enough to inactivate Hepatitis C. Microwaving infected items will heat up any viruses. It’s this that inactivates them.

How hot do you have to heat things up to inactivate Covid-19? Check out our article on the heat requirements for killing Covid-19 here [coming soon!].

Bottom line on microwaving masks to disinfect viruses: Microwaving items that are contaminated with viruses can work to inactivate the virus. Data shows that you should microwave at 600W or higher for at least 2 minutes to deactivate viruses. However, microwaving masks isn’t recommended. It can be tricky and potentially destructive to your mask. You need to first ensure all the metal has been removed from the mask, and be careful that microwaving for 2 minutes doesn’t damage the mask or set it alight.