Does Wearing Surgical Masks With the Wrong Side Out Affect Their Ability to Capture Viruses?

Amid the rush for masks with the coronavirus, we’ve found that some people are wearing masks the wrong way round! But does wearing surgical masks the wrong way round affect their ability to capture viruses?

Some online sources claim it doesn’t matter, like this one.

The wrong way wearing surgical masks

Surgical masks are made up of 3 layers, and there is a specific way to wear them: with the colored, rough-textured side out.

wearing masks right and wrong way

But does the direction you wear it actually affect its ability to capture viruses? Smart Air tested sub-micron particle capture to see whether the orientation of a surgical mask really affects performance.

WATCH: What is the Right Way Round to Wear a Surgical Face Mask

Wearing your surgical face mask WRONG can affect its performance

Testing Surgical Mask Efficiency from Both Sides


To test the surgical masks, we used the same wind tunnel setup that was used for our homemade mask materials tests. In that setup, a fan on one side of a wind tunnel pushes air through the mask on the other end. There, a Met One GT-521 laser particle counter measures how many particles penetrate the mask.

We tested the blue side and white side of four surgical masks.

filteration efficiency tests setup surgical mask

We measured what percentage of particles 0.3 microns and above they could capture. Although the new coronavirus is 0.12 microns on average, scientists sampled air in hospitals and found that SARS-CoV-2 sometimes travels on aerosols from 0.25-0.50 microns.

surgical mask particle size

Read More: Are Wet Masks Less Effective?

Surgical Mask Blue vs. White Side Results

Across four masks, putting the mask in the correct direction improved particle capture by 1.7% on average. On one mask model, the improvement was nearly 3%.

Four masks filtering efficiency for both 2 sides

Although these numbers are pretty small, wearing the mask the right way will increase its effectiveness at capturing virus-sized particles.

Surgical mask correct way side blue effectiveness

Read More: How Effective Are Surgical Masks in Filtering Out Dangerous PM2.5?

Remember: Rough Blue Side Out, Soft White Side In

This data backs up the claim that the colored side of surgical masks (typically blue or green) should face out.Β  The softer white layer should face in.

Bottom Line: Surgical Mask Direction Affects Performance

Wearing surgical masks with the wrong side out decreases filtration of 0.3-micron particles by 1.7% on average.Β  Remember to wear your surgical mask the right way--show the world your colors!

Smart Air

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