What's the best material for a do-it-yourself face mask?
Yang Wang, an assistant professor of environmental engineering at Missouri University of Science and Technology, has some suggestions based on initial testing. He investigated how a few common household materials – such as pillowcases, scarves and furnace filters – filtered out aerosols.
The new coronavirus may survive for a few hours on airborne aerosols and is also spread through larger droplets from a cough or a sneeze.
It turns out that makeshift masks made by layering scarves and bandannas did a poor job of filtering out aerosols.
Hard to breathe
Pillowcase fabric was somewhat better, depending on thread count. A 600-count pillowcase filters better than a 400-count one, Wang pointed out.
But the best aerosol-blocker he tested was from commercially available household air filters. The multi-layered air filters are nearly as effective as an N95 medical mask in blocking aerosols, especially smaller particles, Wang's preliminary findings suggest.
There was a downside, however: As more layers of filter material are stacked, it can be hard to breathe. So, Wang and his team are looking for a combination of materials that filters best with the least interruption in air flow.
And Wang warned that while a furnace filter may be more efficient than a bandanna or pillowcase fabric at blocking aerosols, there may be risks.
Different thread counts
Furnace filters are made of different materials, including cotton, fiberglass or polyester, he pointed out. A protective step would be to wrap furnace filter material with another type of material, such as a fabric.
"There are so many different types of fabric" to consider, Wang said in a university news release. "Even for T-shirts, there are different types of materials. We plan to look at different types of pillowcases, bed sheets and other fabrics with different thread counts."
Wang posted his early test results on 2 April on Twitter.
The US government recently advised Americans to wear cloth face masks to help slow the spread of the coronavirus.