Homemade T-Shirt Masks Block 94% of Airborne Droplets, Study Finds

Since public health officials began recommending the use of face coverings to help prevent the spread of COVID-19, there's been a large discussion on which face coverings are the best at blocking airborne particles that spread the virus. There's a wide variety of options, ranging from surgical masks to hand-sewn cloth face masks. But according to a new study, a mask made from two-layers of T-shirt cloth is able to effectively block most large and small aerosolized particles.

The August study, published in Extreme Mechanics Letters, looked at how well 11 different common household fabrics blocked larger aerosolized droplets that could contain SARS-CoV-2, the virus that causes COVID-19. The researchers also analyzed the breathability of the fabrics (by looking at air permeability), texture, fiber composition, and how well the fabrics absorbed water.

Researchers found that most fabrics block at least 70% of droplets. A mask made of two layers of T-shirt cloth was the most effective, blocking droplets more than 94% of the time. This is similar in effectiveness to surgical masks, but was “twice as breathable,” the researchers wrote.

“Overall, our study suggests that cloth face coverings, especially with multiple layers, may help reduce droplet transmission of respiratory infections,” the researchers concluded. “Face coverings made from materials such as cotton fabrics allow washing and reusing, and can help reduce the adverse environmental effects of widespread use of commercial disposable and non-biodegradable face masks.”

The Case for T-Shirt Fabric

Aerosol particles are usually less than 5 micrometers in size, but larger droplets can also be generated when a person coughs, sneezes, or even speaks, study co-author Taher Saif, PhD, a professor of mechanical engineering at the University of Illinois Urbana-Champaign, tells Verywell. These larger droplets are also an issue because they can squeeze through the pores of some fabric, break down into smaller droplets, and become airborne, he says.

The researchers found that the first layer allowed about 17% of droplets to get through, but significantly reduced the velocity at which those droplets traveled. The second layer then trapped many of the remaining particles.

But, at the same time, “it needs to be breathable," Saif says. "People won’t wear a mask if it’s not."

The study finds that two layers of T-shirt fabric can block droplets from coming in and out while remaining breathable. “It’s amazing material,” Saif says. “It’s affordable, cheap, and comfortable.”

With a double-layer mask made of T-shirt fabric, “the first layer takes the impact of the sneeze droplets, taking away most of the speed and momentum, and lets about half of them go through,” he says. "[But] the second layer blocks almost all of them.”

Cotton fabric also got top marks in a September Duke University study published in Science Advances. Researchers found that, after N95 and surgical masks, three out of the four top face mask performers at blocking respiratory droplets were made of cotton.

Saif says he’s a fan of cloth face masks. “You can wash a cloth face mask. It’s reusable, and they work,” he says. “I have complete confidence in cloth masks.”

Cloth Face Mask Recommendations

The Centers for Disease Control and Prevention (CDC) currently recommends the following for choosing a mask:

• Choose a mask with two or more layers of washable, breathable fabric
• Use a mask that completely covers your nose and mouth
• Make sure the mask fits snugly against the sides of your face without gaps

The World Health Organization (WHO) breaks from CDC guidance, recommending that people choose a mask with at least three layers of fabric. The WHO says that masks that are made up of the following are best:

• An inner layer of absorbent material, like cotton
• A middle layer to act like a filter or barrier, made of a non-woven material like polypropylene
• An outer layer of a non-absorbent material, like polyester or a polyester blend

Both the CDC and WHO recommend against using neck gaiters, a sleeve-like covering, with the CDC saying their effectiveness is unknown at this time.

But wearing any kind of mask is important, Rajeev Fernando, MD, an infectious disease expert in New York, tells Verywell. In fact, data analysis from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington’s School of Medicine found that, if 95% of the people in the U.S. wear masks when leaving their homes, there would be a nearly 49% decrease in COVID-19 deaths in the country.

“Wearing masks save lives and are, for me, the most critical part of preventing COVID-19,” he says.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.