Since COVID-19 started, there has been confusion on how to correctly wear a disposable surgical mask. But does wearing face masks the wrong way round affect their ability to capture viruses?
Some online sources claim it doesn’t matter, like this one.
Surgical masks are made up of 3 layers, and there is a specific way to wear them: with the colored, rough-textured side out.
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.
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.
We measured what percentage of particles 0.3 microns and above they could capture. Although COVID-19 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.
Read More: Are Wet Masks Less Effective?
Surgical Mask Blue vs. White Side Results
Across four masks tested, putting the mask in the correct direction improved particle capture by 1.7% on average. On one mask model, the improvement was nearly 3%.
Although these numbers are pretty small, wearing face mask the right way will increase its effectiveness at capturing virus-sized particles.
Read More: Do DIY Cloth Masks Protect Us From COVID-19?
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. 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. Remember to wear your surgical mask the right way–show the world your colors!
WHAT NEXT?
Along with wearing masks, air purifiers with HEPA filters are also one of the best ways to stay safe from a variety of pollutants in our air including viruses and dangerous PM2.5. A recent CDC study confirmed significantly lower COVID-19 infection rates in schools that used HEPA air purifiers. HEPA filters can significantly lower the risk of a variety of deadly diseases including diabetes, heart disease, cancer, and high blood pressure.
Read More: Four Steps to Choosing the Best Air Purifier
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Am I wearing my mask to stop the spread of infection OR to prevent myself becoming infected?
I wear one to prevent becoming infected, therefore I will continue to wear mine white side out.
Hi Terry, Song here from Smart Air.
White side in will protect the wearer the most from outside viruses. The blue side is designed to repel moisture, so wearing a face mask with the blue side in could lead to quicker mask degradation. We suggest wearing it the recommended way irrespective of which you are trying to protect the most (either the wearer from outside viruses, or other people from the wearer’s viruses).
I’m very confused about this now. In March I got my first mask while entering a hospital for an elective procedure. I am sure that everyone at the hospital, including my surgeon, was wearing the masks with the white side out. I don’t mind being wrong, or having to change, but since EVERYONE I encountered at the hospital, from the screener and the guard at the front door, to the receptionists, to the nurses, and the doctor while performing my surgery had it with the white side out I assumed that was how it’s done.
So white side in catches more viruses particles leaving your body. What if you are healthy? Then wearing the mask white side out, should technically catch more virus particles trying to get in.
White side in will protect the wearer the most from outside viruses. White side out could potentially protect people around the wearer, if the wearer is sick. However we have not tested how moisture from the wearers breath would affect the mask’s effectiveness with the blue side in. The blue side is designed to repel moisture, so wearing a face mask with the blue side in could lead to quicker mask degradation. We suggest wearing it the recommended way irrespective of which you are trying to protect the most (either the wearer from outside viruses, or other people from the wearer’s viruses).
Still no clear! If the blue side repels moisture more effectively, then having it in should result in a lower rate for moisture absorption, thus making it degrade more slowly. Based on the reasoning it should be the other way around.
Hi Yahya, Liz here. We have another article explaining why the layer sequence matters, check it out: https://smartairfilters.com/en/blog/which-way-round-should-i-wear-my-surgical-face-mask/
Your results have no significant test: There is no p-value or confidence intervals in your graphs, thus your ~%1.5 doesn’t mean at all.
Further, I still don’t see any sensible explanation on why the order of different layers/filters should matter!