Fauci said it is 'common sense' to wear 2 masks to stop the spread of COVID-19. Here's how to do it.

• Dr. Anthony Fauci said double-masking is a logical strategy to stop the spread of COVID-19.
• Speaking on NBC News' TODAY, Fauci said double layering "just makes common sense."

Dr. Anthony Fauci endorses double-masking.

US health officials have long been advising people to wear a cloth mask with three layers of protection, or a surgical or N95 mask, to protect against the novel coronavirus.

But some people, including many at the inauguration, have been doubling up on masks - layering them to create an extra barrier of protection.

According to Fauci, it's a good idea, particularly in light of more transmissible variants of the coronavirus, first identified in the UK and South Africa.

Read More: Two face masks may be more protective than wearing one, but it depends on the type and fit

"If you have a physical covering with one layer, you put another layer on, it just makes common sense that it likely would be more effective," Fauci said on NBC News' TODAY. "That's the reason why you see people either double masking or doing a version of an N-95."

How to double-mask

The type of mask you double up on will affect the level of protection it provides.

As Business Insider's Anna Medaris Miller previously reported, it's a good idea to use a surgical mask or an N95 in your layering.

For example, it's better to use a double-layered cloth mask for the outside layer and a disposable surgical mask for the inside, rather than using two single-layered masks together.

The three layers each serve an individual purpose: the outside layer protects against splashes and droplets, the middle layer filters, and the bottom layer absorbs things like saliva and sweat.

Another way to double layer could be using a two-layered cloth mask with a face shield on top, though there is some evidence that masks may be more protective than shields.

Double layering doesn't mean you should let your guard down. Public health officials say the general public should still use social distancing practices, wash their hands regularly, and avoid gathering indoors.