- A face mask experiment shows precisely why this particular piece of personal protective equipment is a key tool for reducing the risk of coronavirus transmission.
- One doctor conducted the same test with and without a face mask to prove how many microorganisms a person can eject when sneezing, coughing, singing, and just talking.
- The experiment showed that a face mask can significantly reduce one’s exposure to the virus, thus minimizing the risk of contracting COVID-19.
Every single person can do three things to reduce the risk of catching the novel coronavirus. That’s washing your hands often, avoiding crowds and sticking to social distancing practices, and using face masks every time you’re out. Neither one is perfect and there’s no such thing as 100% protection against infection. But this combination may be enough to reduce the risk of transmission dramatically. Of all three measures, face masks became a huge point of contention in recent weeks. Rather than appreciating this simple tool that can potentially save lives, some people question the political motives behind mandates to use masks. The face mask turned into a political tool rather than a must-have piece of PPE that can prevent the spread of COVID-19. It’s not just in the US where some people offer senseless resistance to face masks, it’s a movement seen elsewhere as well.
There’s no denying that the science behind face masks works and they can indeed stop the spread of microorganisms. Don’t believe it? A doctor went ahead and conducted a very simple experiment to prove how efficient face masks can be when dealing with a pandemic.
“What does a mask do? Blocks respiratory droplets coming from your mouth and throat,” Dr. Rich Davis said on Twitter, where he posted a simple demonstration that shows the principle of the face mask.
What does a mask do? Blocks respiratory droplets coming from your mouth and throat.
Two simple demos:
First, I sneezed, sang, talked & coughed toward an agar culture plate with or without a mask. Bacteria colonies show where droplets landed. A mask blocks virtually all of them. pic.twitter.com/ETUD9DFmgU
— Rich Davis, PhD, D(ABMM), MLS 🦠🔬🧫 (@richdavisphd) June 26, 2020
He held an agar culture plate about a foot away from his face and then he sneezed, sang, talked, and coughed twice at it. He did the same thing while wearing a mask and then he posted the results. Agar culture plates are used in microbiology to grow various cultures of pathogens. Davis is the clinical microbiology lab director at Providence Sacred Heart Medical Center in Spokane, Washington, so he’s clearly in a position to know precisely how these Petri dishes work.
Unsurprisingly, the plates that were exposed to germs ejected from Davis’s mouth grew significantly more bacteria, as seen in the image below. The agar dishes that were protected by his mask clearly illustrate the mask’s effectiveness. There’s almost no visible trace of bacterial growth in most of them, compared to the plates that were exposed directly to Davis.

Bacteria, of course, is different from viruses — but the point is the same. A face mask can protect both the wearer and the people nearby. Plenty of research demonstrates how easy it is for droplets to travel in the air from sneezes, coughs, and even regular speech, and how they can turn into virus-carrying aerosols that linger in the air. A face mask can reduce the risk of transmission while you’re sharing the same space with other people, whether it’s at work, the grocery store, or anywhere else.
Also, the fact that Davis was holding the culture plates so close to his face highlights the importance of social distancing. The closer you are to a person, the higher the risk of transmission.
We saw research in the past few months that also showed how a single infected individual spread the virus to 52 other people from the same choir group, after a singing session that lasted less than three hours. Separately, contact tracers from China determined that the member of a family transmitted the virus to people sitting at three different tables in a restaurant setting, including members of their own family. Both these examples come from a time when the coronavirus threat was still underreported or minimized. And given the settings, it’s unlikely that people were wearing face masks while eating or singing.
Davis’s experiment should help people explain how easy it is for a person to spread bacteria and viruses around them, and to protect themselves from the same germs.