Mask Test

Scientists identify the best (and worst) Covid-19 masks

Laser beam experiments reveal masks that are nearly perfect, and one that raises concerns.

Mask wearing is an essential part of controlling the spread of coronavirus.

New research shows that some masks are far more effective than others.

Kilito Chan/Getty Images

Scientists at Duke University put 14 common masks through their paces...

Brown University/Giphy

The 15 masks used in the experiment ranged from surgical masks to gaiters. All masks were tested once, but bandanas, surgical masks, and a 2-layer pleated cotton mask (#13) were tested four times.

Correction: Gaiters were tested on one participant, not four, as previously stated.

The team used a laser-beam experiment to show how many droplets were released when people spoke the phrase "stay healthy, people" five times in ten seconds.

Youtube/Duke Health

The masks were fit "as a normal person would wear them," Martin Fischer, a study co-author, tells Inverse.

While wearing no mask (a control), one participant released about 960 droplets.

The amounts of droplets varied — some speakers only released 200.

Other studies suggest that 1 minute of speaking can release over 1,000 droplets.

The two worst masks:

Fleece or Gaiter

14th place

Science Advances

Fleece or Gaiter

Fleeces (gaiters) released more droplets (orange) than wearing no mask at all (green).

The team suggests that's because large droplets are broken up into smaller droplets by the gaiter.

Science Advances

Because small droplets remain airborne longer, "the use of such a mask might be counterproductive," the team writes.

Key to understanding this result is knowing that they found wearing a gaiter to be "counterproductive" in this experiment on just one person. More robust research is needed to make any conclusions about this type of mask.

Bandanas

13th place

Science Advances

Bandanas

Bandanas released about 50 percent as many droplets compared to wearing no mask at all.

Science Advances

The two bests masks:

Brown University/Giphy

Fitted N95

1st place

Science Advances

Fitted N95

Fitted N95 masks released less than 0.1 percent of droplets (orange, not visible) that would have been spewed if no mask was worn (green).

Science Advances

Surgical masks

2nd place

Science Advances

Surgical masks

Surgical masks released only about 1 percent of droplets (orange) that would have been released if no mask was worn (green).

Science Advances

Honorable Mentions...

Brown University/Giphy

Cotton-polypropylene-cotton masks and 2-layer polypropylene apron masks both only allowed between 5 percent and 10 percent of the droplets through, compared to wearing no mask.

Science Advances

Cotton-polypropylene-cotton masks (light green) took 3rd place.

2-layer polypropylene apron masks (dark green) took 4th place.

Science Advances

The middle of the pack...

Brown University/Giphy

Several different varieties of cotton masks, valved N95 masks, and knitted masks all allowed between 10 percent and 50 percent of droplets to escape.

Science Advances

Knitted masks fared the worst of this group (red, 12th place).

Two-layer cotton pleated masks (yellow, 5th and 6th place) performed the best.

Science Advances

This experiment is only meant to be a proof-of-concept.

The takeaway, says Fischer is simple.

Youtube/ Duke Health

"A mask for the general public doesn’t have to be perfect – most masks work!"

Youtube/ Duke Health

Read more about how to get the most out of your mask here.

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