Do Carbon Filters in Face Masks Offer More Protection Against Coronavirus?

Cloth face masks can help slow the spread of coronavirus. But do they need filters, too?
Cloth face masks can help slow the spread of coronavirus. But do they need filters, too?
JohnnyGrieg/iStock via Getty Images

Through the winter, spring, and summer of a global pandemic, many people have gotten used to the idea of wearing a cloth face covering to reduce the spread of the coronavirus, the highly infectious virus looking to find as many human hosts as possible. Masks both inhibit the distribution and inhalation of respiratory droplets, which can carry the virus.

Recently, a number of homemade and mass-produced cloth face masks for sale online have boasted of having a carbon or other kind of filter in place that might improve the efficacy of the mask, warding off even more viral particles than the mask alone. Can this additional filtration really help?

According to health experts, the answer is yes—but you should exercise caution in what type of filter you choose.

Filters are typically sandwiched between two layers of cotton. Alternately, a mask provider might offer a mask with a pocket for a filter of your choosing. Some filters claim to be HEPA-certified, a standard for air filtration, or made with carbon, which may increase the potential for particulates to stick to the material, blocking it from entering or exiting the mask. But while these filters are used in air filtration devices, their effectiveness has yet to be evaluated when worn on the face.

“Carbon and charcoal are meant to filter contaminants from water,” May Chu, Ph.D., a clinical professor of epidemiology at the Colorado School of Public Health Anschutz Medical Center, tells Mental Floss. “We don’t know if breathing in charcoal fragments or particles is good for your lungs.”

The same holds true for using vacuum cleaner bags or coffee filters. Some, Chu says, are made with silica fibers, or glass. That’s not anything you want in your lungs. “These are not designed for breathing,” Chu says.

According to Chu, the most important feature of a mask is that it hits the “sweet spot” of locking in particles while maintaining comfort and breathability. If a mask is very thick, you’re not likely to inhale droplets through it, but you might have trouble with air passing through it and would likely wind up inhaling through the open sides, where there’s no barrier.

Cotton is the preferred mask material. A tight weave cotton allows for air flow and tends to trap particles better than synthetic materials, which have a smoother structure. Cotton also tends to work best with one or more layers depending on whether you can see light shine through it. If you can, it’s too thin.

Because cotton isn’t intrinsically designed to protect against particles, there is value in adding a filter. But like the mask itself, it needs to be made of a safe material that’s comfortable to wear. Chu recommends polypropylene, a material that can be purchased under the brand name Oly-Fun from Walmart and other retailers and is also sold under the name Spunbond.

Polypropylene is sold under the brand name Oly-Fun. Walmart

What’s so special about polypropylene? “It’s the same material used in N95 masks,” Chu says. The N95 mask is used by medical professionals and filters up to 95 percent of airborne particles. But Chu cautions that consumers need to be aware that there are differences between store-bought polypropylene and the kind used in a medical-grade N95.

“The quality of the N95 polypropylene is calibrated and designed for a particular level of filtration that has a standard,” she says. “It’s more expensive and tooled more precisely.” Two layers of Spunbond polypropylene can approach—though not duplicate—the protective qualities of a single layer of the medical quality mask filters.

Polypropylene is effective because it can hold a static charge that repels particles. While an N95 mask is made to hold that charge for the life of the mask, you can generate a charge with a homemade filter by ironing the polypropylene or rubbing it with a plastic glove for 20 seconds. The charge will last for roughly 12 hours or until it’s washed, Chu says.

If polypropylene isn’t available, there’s an alternative that virtually anyone can use. Simply stuff four sheets of Kleenex (or two sheets folded in half) into the pocket of the mask. “The Kleenex gives you good efficiency in blocking particles and breathability,” Chu says.

No matter which filter you use, it’s important to remember that once a mask or filter gets wet, it loses its ability to hold a charge (for polypropylene) or block particles (facial tissue). The filter needs to dry or be switched out in order to maintain its effectiveness.

Obviously, medical professionals opt for an N95 when they’re available. But what does Chu do when it’s time to wear a cloth mask? “I wear a mask that’s locally made,” Chu says. “It’s two layers of polypropylene pocketed by cotton in the front and back.”

Coupled with social distancing and hand washing, a breathable mask with a safe filter can slow the spread of the virus, reducing infectious droplets that come out of a person’s mouth. “That’s why masks are good,” Chu says. “That’s what we know works.”

The 10 Best Air Fryers on Amazon


When it comes to making food that’s delicious, quick, and easy, you can’t go wrong with an air fryer. They require only a fraction of the oil that traditional fryers do, so you get that same delicious, crispy texture of the fried foods you love while avoiding the extra calories and fat you don’t.

But with so many air fryers out there, it can be tough to choose the one that’ll work best for you. To make your life easier—and get you closer to that tasty piece of fried chicken—we’ve put together a list of some of Amazon’s top-rated air frying gadgets. Each of the products below has at least a 4.5-star rating and over 1200 user reviews, so you can stop dreaming about the perfect dinner and start eating it instead.

1. Ultrean Air Fryer; $76


Around 84 percent of reviewers awarded the Ultrean Air Fryer five stars on Amazon, making it one of the most popular models on the site. This 4.2-quart oven doesn't just fry, either—it also grills, roasts, and bakes via its innovative rapid air technology heating system. It's available in four different colors (red, light blue, black, and white), making it the perfect accent piece for any kitchen.

Buy it: Amazon

2. Cosori Air Fryer; $120


This highly celebrated air fryer from Cosori will quickly become your favorite sous chef. With 11 one-touch presets for frying favorites, like bacon, veggies, and fries, you can take the guesswork out of cooking and let the Cosori do the work instead. One reviewer who “absolutely hates cooking” said, after using it, “I'm actually excited to cook for the first time ever.” You’ll feel the same way!

Buy it: Amazon

3. Innsky Air Fryer; $90


With its streamlined design and the ability to cook with little to no oil, the Innsky air fryer will make you feel like the picture of elegance as you chow down on a piece of fried shrimp. You can set a timer on the fryer so it starts cooking when you want it to, and it automatically shuts off when the cooking time is done (a great safety feature for chefs who get easily distracted).

Buy it: Amazon

4. Secura Air Fryer; $62


This air fryer from Secura uses a combination of heating techniques—hot air and high-speed air circulation—for fast and easy food prep. And, as one reviewer remarked, with an extra-large 4.2-quart basket “[it’s] good for feeding a crowd, which makes it a great option for large families.” This fryer even comes with a toaster rack and skewers, making it a great addition to a neighborhood barbecue or family glamping trip.

Buy it: Amazon

5. Chefman Turbo Fry; $60


For those of you really looking to cut back, the Chefman Turbo Fry uses 98 percent less oil than traditional fryers, according to the manufacturer. And with its two-in-one tank basket that allows you to cook multiple items at the same time, you can finally stop using so many pots and pans when you’re making dinner.

Buy it: Amazon

6. Ninja Air Fryer; $100


The Ninja Air Fryer is a multipurpose gadget that allows you to do far more than crisp up your favorite foods. This air fryer’s one-touch control panel lets you air fry, roast, reheat, or even dehydrate meats, fruits, and veggies, whether your ingredients are fresh or frozen. And the simple interface means that you're only a couple buttons away from a homemade dinner.

Buy it: Amazon

7. Instant Pot Air Fryer + Electronic Pressure Cooker; $180

Instant Pot/Amazon

Enjoy all the perks of an Instant Pot—the ability to serve as a pressure cooker, slow cooker, yogurt maker, and more—with a lid that turns the whole thing into an air fryer as well. The multi-level fryer basket has a broiling tray to ensure even crisping throughout, and it’s big enough to cook a meal for up to eight. If you’re more into a traditional air fryer, check out Instant Pot’s new Instant Vortex Pro ($140) air fryer, which gives you the ability to bake, proof, toast, and more.

Buy it: Amazon

8. Omorc Habor Air Fryer; $100

Omorc Habor/Amazon

With a 5.8-quart capacity, this air fryer from Omorc Habor is larger than most, giving you the flexibility of cooking dinner for two or a spread for a party. To give you a clearer picture of the size, its square fryer basket, built to maximize cooking capacity, can handle a five-pound chicken (or all the fries you could possibly eat). Plus, with a non-stick coating and dishwasher-safe basket and frying pot, this handy appliance practically cleans itself.

Buy it: Amazon

9. Dash Deluxe Air Fryer; $100


Dash’s air fryer might look retro, but its high-tech cooking ability is anything but. Its generously sized frying basket can fry up to two pounds of French fries or two dozen wings, and its cool touch handle makes it easy (and safe) to use. And if you're still stumped on what to actually cook once you get your Dash fryer, you'll get a free recipe guide in the box filled with tips and tricks to get the most out of your meal.

Buy it: Amazon

10. Bella Air Fryer; $52


This petite air fryer from Bella may be on the smaller side, but it still packs a powerful punch. Its 2.6-quart frying basket makes it an ideal choice for couples or smaller families—all you have to do is set the temperature and timer, and throw your food inside. Once the meal is ready, its indicator light will ding to let you know that it’s time to eat.

Buy it: Amazon

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

Does Putting a Penny in the Microwave Really Make It Shrink?

J E Theriot, Flickr // CC BY 2.0
J E Theriot, Flickr // CC BY 2.0

It's a lesson even the worst home cooks (hopefully) know: Putting metal in the microwave is a recipe for disaster. Thanks to a viral image circulating on the web, some people may be tempted to ignore this piece of common sense in the name of experimentation. The picture shows one normal-sized penny next to three smaller pennies with the caption: "This is what happens when you put a penny in a microwave for 2 minutes." But according to Snopes, microwaving a penny won't cause it to shrink—if anything, it will just leave you with a broken microwave.

Microwave ovens heat food by bouncing microwaves around a metal box. Certain molecules, like the molecules in your leftovers, absorb these waves via dielectric loss and convert them into heat. Not all substances are compatible with microwaves, however. Metal contains high concentrations of electrons, and when microwaves hit a metallic surface, these electrons become very active and block the wave's path. Instead of absorbing into the metal, the microwaves bounce off, which can cause electrical sparks. Sometimes these sparks are strong enough to burn a hole in the oven's walls and damage the electronic equipment.

Even if you could somehow shrink coins in a microwave, the science explained above should be reason enough to resist the urge to try it at home. Anyone who tries the experiment against their better instincts will be disappointed. The photo that's been shared on social media is a hoax, with Snopes explaining that the smaller pennies likely originated in a magician's trick kit.

The post inspired some people to share false claims of their own. One response to the image showed a melted microwave that had allegedly fallen victim to the penny trick. In reality, the years-old picture came from a blogger who set their microwave on fire accidentally while heating a pot of oil. So while microwaving a penny may cause some sparks and potentially damage your appliance, a dramatic explosion isn't likely. (Please just take our word on that, too.)

[h/t Snopes]