Now, the CDC is saying that we should all wear homemade cloth masks.

And luckily for us, groups of scientists have been testing which materials work best for homemade masks,

and have some preliminary results.

But first of all, I do just wanna clear this up—

until now, the CDC only recommended masks for people who are sick or for healthcare workers,

and this is still the WHO's guidance.

This seems primarily to be because these organizations were concerned about people hoarding

or stockpiling masks

when healthcare workers are the ones who desperately need them.

This especially applies to N95 respirators,

which are a specialized face coverings that when worn properly,

filter out 95% of particles down to 0.3 microns in size,

and can reduce the likelihood of contracting a contagious respiratory disease.

So, what about the rest of us?

Well, most countries still advise that there isn't enough robust evidence to suggest that a cloth mask

or even a regular surgical mask significantly protects you from becoming infected by this virus.

Some kind of mask can be better than no mask at all, depending on the circumstances,

but the main purpose of these masks is not to prevent you from getting sick…

it's to prevent sick people from getting other people sick.

The CDC's new recommendation is that everyone should now be wearing a homemade mask

when out and about—not just sick people.

And that's because several new anecdotal studies about the transmission of COVID-19

indicate that there may be significant community spread of the disease

before someone shows symptoms

or from people who never show symptoms at all.

Even though there isn't yet solid evidence to suggest that cloth face coverings

combat asymptomatic shedding of the virus,

the CDC's policy has now shifted to say, Okay, let's all wear a mask so that even if we don't feel sick,

we still may reduce our likelihood of making someone else sick while we're out and about.'

Now, the literature on how well different homemade masks block particles, or aerosols, or droplets—

both from coming in and from getting out—is...pretty sparse.

In response, teams of scientists all over the country are now informally trying to determine

how good certain materials are at blocking droplets and particles,

and are sharing their research publicly.

The key is to find a material or combination of materials that blocks particles,

but that you can still breathe through—y'know, because that's pretty important.

Early results from a team at the Missouri University of Science & Technology were shared on Twitter recently.

They tested different kinds of air filters, like furnace filters and HVAC filters,

that in two layers created 94% filtering efficacy,

and in 6 layers, got to 95% filtration.

But, these filters are not made to be worn directly next to your face

and could shed particles that would be harmful to breathe in directly.

So, if you do want to use a filter like this,

you should sandwich it between two layers of fabric, like a t-shirt or a bandana.

This group also tested some common fabrics.

Four layers of a 600 thread count sheet filtered out 60% of microparticles,

two layers of a thick woolen scarf filtered out 48.8%,

three layers of coffee filters filtered out up to 50%—

but turned out to be much less breathable—

and a cotton bandana by itself only filtered out 19.5%...even with four layers.

Other tests out of the Wake Forest Institute for Regenerative Medicine

indicate that high thread-count quilting cotton in a double layer

can perform as well or better than a standard surgical mask,

but they also caution that homemade masks using a less sturdy fabric

had filtration rates as low as 1%,

so you definitely need to choose your materials wisely.

And if you're not into sewing, no problem!

There are also patterns online for folding materials like vacuum bags into origami-like masks.

Depending on the material used, these can filter between 60-87% of particles.

But again, be super careful here, and make sure the filter you choose is made of material that's safe to breathe.

You've got to look at the ingredients.

And even though this research effort is really cool, there are a lot of caveats.

These results have not been formally peer-reviewed or published.

And it also needs to be said that these filtration rates I just mentioned are from highly controlled conditions

that tested just the materials by themselves,

and didn't test for protection for the actual coronavirus, just particles of a certain size.

When worn in a mask-form on someone's face,

how much particulate matter actually gets filtered depends on if you're wearing the mask properly.

The CDC recommends that your homemade mask cover your mouth and nose

and sit really snugly against your face with as little gapping as possible—

like no air should be getting in there.

They also recommend that the mask be secured with a tie or ear loops to keep it in place.

And you have to remember that reducing your risk of infection is still hugely dependent on

not touching your mask and your face with unwashed hands,

so think really carefully before you adjust it.

To top it all off, we're still waiting for more guidance from the CDC on how often to change your mask

if it gets saturated,

if homemade masks can be sterilized and reused—and if so, how?

So, it's very likely that mask recommendations will continue to evolve.

The bottom line here is: wearing a mask can slow the spread of this disease

by keeping actively sick people from infecting other people.

But it doesn't protect you from becoming infected as much as it protects other people from you,

so don't use as mask as license to go crazy and stand too close to someone in line at the grocery store

or not cover your sneeze.

Masks can give you a false sense of security,

but social distancing and hand-washing are still the #1 tactics for slowing this pandemic.

The use of masks may just tip the odds a little more in our favor

as we learn more about how the disease spreads.

If you want more of our coronavirus coverage, check out this video here,

and subscribe to Seeker to stay up to date with all your health news.

Thanks so much for watching, stay safe out there, and I'll see you next time.