Ask Dr. Universe: Masks are more effective than shields

Dr. Universe,

What is more effective against coronavirus, a face mask or a face shield?

— Rhma, 9, Washington

If you are like me, you’ve probably seen people wearing face masks, face shields or even both at the same time.

To find out more about your question, I talked to my friend Armine Ghalachyan, a researcher at Washington State University. She’s curious about how apparel, including face masks, can help people in our world.

First, she said it helps to think about how a virus spreads. When humans laugh, talk, cough and sneeze, they release tiny droplets into the air. A single sneeze has been shown to release around 40,000 droplets.

These droplets are made up of mucus and saliva from our nose and mouth — and they are just the right travelling size for a virus like SARS-CoV-2, which causes the novel coronavirus.

When people design face masks they think about these droplets. They research what materials work best to help block out droplets that might contain a virus that can make us sick. But it’s not just a question of material. They also have to think about how masks fit on our faces.

Face shields are not as effective as face masks, according to the Centers for Disease Control and Prevention. While face shields may provide some eye protection, they leave a lot of gaps around the face. That makes it easier for a person to pass droplets that might contain the virus to other people. There’s also not much material there to keep the person wearing a shield from breathing in other people’s droplets.

Meanwhile, facemasks that fit over the nose, mouth and cheeks can help keep droplets from spreading around. One type of mask, an N-95, is made up of material called polypropylene, and blocks 95 percent of tiny particles. People, including healthcare workers, who wear these masks often do a fit test.

For instance, in one test, a person puts on a mask and then puts on a suit with a plastic hood where they are asked to smell or taste things like bitter scents. If the mask fits well, they shouldn’t be able to taste or smell anything. That’s one way we can test if the mask is doing its job to block out tiny particles.

Some masks made of cotton threads that are woven tightly together can also help block droplets. Those crisscrossing threads that make up the fabric can help keep a virus from passing through the material. Since a virus will often enter the body through the nose and mouth, which are connected, it is important to cover them both.

It takes not only the right material but also a proper fit to help a face mask do its job the best. Finally, it’s important to remember that while vaccine trials are still underway for children under 12, properly wearing a face mask, handwashing and social distancing are the most effective tools we have to stay safe and healthy.

P.S. Do you know an 8-12 year old student with questions about volcanoes, earthquakes & geology? Submit the question for a chance to be featured in an upcoming YouTube video at askDrUniverse.wsu.edu/ask

Have a science question? Ask Dr. Wendy Sue Universe, WSU’s resident science cat and writer, by email at Dr.Universe@wsu.edu.