Coronavirus FAQ: What Does It Mean If I Can Blow Out A Candle While Wearing A Mask?

Each week, we answer "frequently asked questions" about life during the coronavirus crisis. If you have a question you'd like us to consider for a future post, email us at goatsandsoda@npr.org with the subject line: "Weekly Coronavirus Questions."

Can you blow out a candle with your mask on?

That question became ... a thing ... this month when Bill Nye (aka "The Science Guy") made a TikTok.

In it, he dons various types of masks that people are using during the pandemic to, as he puts it "prevent particles from my respiratory system from getting into the air and then into your respiratory system" — in other words, a way of limiting transmission of viral particles. Nye attempts to blow out a candle about a foot away — a simulation for everyday respiratory exchanges and interactions like coughs and conversations.

Most of his masks do the job (except for a knitted scarf), though in other versions of this experiment and in tests conducted by NPR mask wearers, a bandana over the mouth usually d allowed the wearer to extinguish the flame.

Basically, you want the flame to stay alive, says Amy Price, a senior research scientist at Stanford's Anesthesia Informatics and Media Laboratory. Otherwise, it can be a sign that the mask isn't acting as a strong enough barrier. If you can blow out the flame easily while wearing a mask, she says, there's too much air exchange between you and the outside world.

Still, she cautions that the test isn't foolproof. Outside variables, like the type of candle and your personal lung strength can affect the outcome. So take your results with a big, big grain of salt, Price says.

Harvard Medical School physician Dr. Abraar Karan notes: "Being able to blow a candle out may be some measure of how well particles can exit your mask, [but it's] unclear to me how reliable that is as a proxy for small aerosols exiting with normal speaking or coughing."

Nonetheless, Price believes the candle test can be a good way to suss out the masks that are clearly not doing their job — aka the dead giveaway cases.

"It's an OK rule of thumb," she says. "It isn't scientific, but it's a pretty good estimate, especially when you combine it with other [tactics] and recommendations" regarding mask quality.

So what's in an effective mask?

A group of researchers at Stanford Medicine is working with the World Health Organization to figure just that out—the team has helped roll out new guidelines for mask efficacy and safety along with WHO. And even they agree that for most people, identifying a good, protective mask from a bad one can be confusing.

"People have no standards when they go to buy masks," says Price, who is a member of the team.

And it's not as if you can test the mask yourself. Renting mask-testing equipment costs over $1,000 and it's not as if such devices are on the shelf in your neighborhood medical equipment store.

To make sure you're not flying mask-blind, it's important to keep abreast of WHO and Centers for Disease Control mask guidelines, which are regularly updated. Right now, Price says masks with three layers are the recommendation.

And there are some mask facts and hacks that can be helpful.

Karan says one of the most fundamental things to get right about your mask is fit.

You want your mask to fit snugly over your mouth and nostrils, up to the nose bridge, with little excess air escaping from the sides when you exhale. But you also want to be able to breathe, he explains. A good rule is as snug as you can go without finding it hard to breathe.

Make sure you get this right, he urges. One study found that "gaps due to improper fit resulted in over a 60% decrease in the filtration efficiency."

Then there's the question of mask material.

Price suggests two ways to test if your mask is crafted with a good weave: You can pick up a Foldscope microscope (they're made of paper and cost about $30 for a DIY kit) to zoom into the texture of the mask — the weave should look thick and relatively opaque.

Or you can also just hold your mask up to a bright light source or use your phone flashlight. "Stretch it," recommends Price. "Can you see right through it?" If you can, that's a bad sign.

You can also check labels for preferable fabrics and materials; recent studies have shown that 100% cotton with high to moderate yarn count (AKA, a heavier, coarser yarn) performed best in mask tests conducted, Karan says. While the process for figuring out yarn count can be a little tricky, the general rule is the thicker the fabric, the higher the yarn count.

"In short, you want a mask that fits you well, and that has cotton with high yarn counts and possibly with multiple layers which many masks today do offer," Karan says.

Once you've found a great-fitting mask fashioned with a breathable and protective material, Price says her lab has identified some simple DIY steps to fortify your mask.

"You can make a small slit (between mask layers) and add paper towels," Price offers. "Or buy yourself some OLY fun (a craft product) and place a layer in the mask — this can bring it up to a surgical mask's level of protectiveness."

Adding a static charge to the outer layer of a polyester mask by rubbing it with a latex glove for 30 seconds can also be effective, Price adds. The reason: COVID-19 particles have a charge, so adding static can help create an extra layer of repelling protection.

With the surge in mask demand, there are also new market conditions to navigate.

"If you're going to buy a mask, look at it carefully, Price says. "Don't buy things that claim to be 'specially treated" with copper or other irons that kill bacteria." The virus isn't bacterial, and those treatments haven't been proven to be effective with the novel coronavirus as of yet, she says.

Finally, if you want to make a homemade mask, Price emphasizes the power of improvisation and creativity.

Indeed, research shows that even the most surprising materials — like a pair of pantyhose — can boost the power of your mask.

Pranav Baskar is a freelance journalist and U.S. national born in Mumbai. [Copyright 2020 NPR]