Different Kinds of Masks: Effectiveness Examined by Physicists

We’ve all seen people wearing many types of masks. Some wear them below their nose, others look like they are wearing a mask that hasn’t ever been washed or replaced. What is effective, what isn’t?

The L.A. Daily News on July 12 ran a piece titled “Mask Effectiveness.” They cited research from Florida Atlantic University’s College of Engineering and Computer Science that was published in the journal Physics of Fluids.

Physicists accessed the effectiveness of face masks, using emulated coughs and sneezes to examine the material- and design-choice impact on the extent to which droplets are blocked.

Without a face mask, droplets traveled more than eight feet; with a bandana they traveled three feet, seven inches, with a folded cotton handkerchief, they traveled one foot, three inches; with a quilted cotton mask they traveled 2.5 inches and with a cone-style mask, droplets travel about eight inches.

The authors of the piece wrote: “Leakage remains a likely issue for members of the general public, who often rely on loose-fitting homemade masks. Additionally, the masks may get saturated after prolonged use, which might also influence their filtration capability. We reiterate that although the non-medical masks tested in this study experienced varying degrees of flow leakage, they are likely to be effective in stopping larger respiratory droplets.”

The most efficient masks were the N95. (The study, which was published online on June 30, can be found by visiting: aip.scitation.org “Visualizing the effectiveness of Face Masks in Obstructing Respiratory Jets.”)

The Daily News also included quotes from a June 2 Live Science story (visit: livescience.com/are-face-masks-effective-reducing-coronavirus-spread.html). For example, “Putting a face mask on does not mean that you stop the other practices,” said May Chu, a clinical professor in epidemiology at the Colorado School of Public Health on the Anschutz Medical Campus.

“One thing everyone does agree on is that, whatever containment provided by non-fitted masks do provide, homemade fabric masks are the least effective,” Chi said. “The recommendations that everyone wear masks are because ‘any kind of impediment is better than nothing.’ But fabric masks are not expected to be as protective as surgical masks. That’s why public health officials are warning people to remain at least 6 feet apart from one another, even if they are wearing masks. In other words, homemade masks are likely to be just a small piece of the puzzle for controlling the COVID-19 pandemic.”

In that article, Ben Cowling, head of the Division of Epidemiology and Biostatistics at Hong Kong University, told Live Science that “There’s been enough research done to be able to confidently say that masks wouldn’t be able to stop the spread of infection, that they would only have a small effect on transmission. We shouldn’t be relying on masks to help us go back to normal.”

Yet still, masks are an important element in the battle against Covid-19. So please wear a mask at appropriate times.

N95 masks are effective at stopping virus transmission. Cloth and loose-fitting homemade masks are not so efficient and may allow leakage.

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