Demonstration Shows How Masks Block Droplets

Dr. Rich Davis, the Clinical Microbiology Lab Director at Providence Sacred Heart Medical Center in Spokane, Washington, recently demonstrated how surgical masks can block respiratory droplets. The demonstration showed, in stark contrast, the amount of droplets that can spread from a person’s nose and throat as aerosols when they’re wearing a surgical mask versus not wearing one. The results of the surgical mask demonstration were so stark, in fact, that they have gone viral online.

Davis recently posted the results of his surgical mask demonstration to Twitter, showcasing two sets of agar culture plates side by side. Davis notes that he coughed, spoke, sneezed and sang at one set of plates with a surgical mask on, and did the same with another set of plates without wearing a mask. (Agar culture plates are Petri dishes that utilize agar, which is a jelly-like substance obtained from red algae, to culture microorganisms.)

After placing the agar plates in an incubator for 24 hours, Davis pulled them out and found that the no-mask group of plates contained, at least visibly, far more bacterial growth than the one associated with surgical mask usage. The differences between the amount of bacterial growth shown between the plates were most noticeable when it came to sneezing and coughing. (There was no control group.)

Davis, who says he’s received a response from people “like nothing [he] could’ve expected,” does make it clear that this is just a demonstration. The lab director notes that this demonstration “isn’t how you culture viruses or model spread of SARS-CoV-2,” but he does does say that it shows how masks can mitigate the spread of large, respiratory droplets.

“These spots on the plates we’re seeing, those are colonies of thousands of millions of bacteria that have just divided enough and [multiplied] enough that we can actually visually see them on the plate,” Davis told a reporter from KHQ. Davis repeated the demonstration with the reporter, who also coughed, sang, sneezed, and talked at a pair of agar plates with and without wearing a surgical mask. The same results were achieved.

On top of noting that this is not how viruses are cultured, Davis also highlighted that this demonstration, of course, does not compare the efficacy of different mask types. The microbiologist does say, however, that he thinks you could test different masks with the same setup, and would likely achieve similar results.

For those looking for the current, official guidelines regarding medical mask usage in the context of COVID-19, below is the WHO’s recommendation as of June 5.

What do you think about this surgical mask demonstration by Dr. Rich Davis? Does this demonstration impact your thoughts regarding surgical masks and COVID-19? Let us know in the comments!

Feature Image: 2C2K Photography