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Here are the five most effective face mask styles according to science

Bad news for people wearing bandannas and fleeces and even worse news for those around them.

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Researchers at Duke University are using a novel method to judge the effectiveness of different styles of face mask.

Using a setup consisting of a box, a laser, a lens, and a cell phone camera, chemist and physicist Martin Fischer was able to devise a system for counting the number of particles expelled from each type of mask as they repeated the phrase, "Stay healthy, people."

Particles being captured by light reflected from the laser.
Masks tested in the experiment

Ditch the fleece

Fischer's experiment, which appeared in a proof-of-concept in Science Advances, turned up several interesting findings, including some disconcerting evidence regarding fleece masks.

Experiments suggest fleece masks could potentially be worse than wearing no mask at all. When droplets were ejected through fleece, they became finer which caused them to increase in number and disperse more erratically.

Using the method, researchers were able to rank 14 different types of mask in order of how well they block the spread of droplets expelled from one's mouth.

Here are the top five according to research...

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5. Swath

A "swath" mask made of polypropylene came in at number five. Researchers appear to have tested a mask with ear loops made out of a single layer of polypropylene, which is commonly used in surgical masks.

4. Two-layer polypropylene

Polypropylene is a polymer used commonly in household plastics (think the top of a TicTac box) and also happens to the material of choice when it comes to making surgical masks.

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3. Polypropelene/cotton

The cotton-polypropylene-cotton mask was the third best performer out of the list. This material combination is typically used for disposable masks with some added breathability from the cotton.

2. Surgical mask with three layers

The common surgical mask (at least those with three layers of material) ranked almost at the top of researchers' list. Multiple layers and mask shape prevent almost all droplets from escaping.

1. Fitted N95 with with no respirator

Unsurprisingly, N95 masks were at the top. According to the CDC, N95 masks are fitted to cover the face seamlessly and filter out 95 percent of airborne particles. This mask has no respirator which helps prevent droplets from entering and escaping.

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The rest of the rankings...

6. Cotton 5 (2-layer cotton, pleated style mask)

7. Cotton 2 (2-layer cotton, pleated style mask)

8. Valved N95 (N95 mask with exhalation valve)

9. Cotton 4 (2-layer cotton, Olson style mask)

10. MaxAT (1-layer Maxima AT mask)

11. Cotton 1 (1-layer cotton, pleated style mask)

12. Cotton 3 (2-layer cotton, pleated style mask)

13. Knitted (Knitted mask)

14. Bandana (Double-layer bandana)

15. 'None' (Control experiment, no mask)

16. Fleece

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Though some masks are clearly better at blocking the spread of droplets, researchers were clear that wearing a face covering (one that's not made of fleece at least) is a critical part of preventing the spread of infectious diseases like COVID-19.

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“If everyone wore a mask, we could stop up to 99% of these droplets before they reach someone else... In the absence of a vaccine or antiviral medicine, it’s the one proven way to protect others as well as yourself.”

Eric Westman, Duke Physician

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