With the pandemic still raging and several dangerous variants looming, many experts have suggested doubling masks. Now, a new study by the Centers for Disease Control and Prevention is doubling that strategy.
Adding a cloth mask over a surgical mask on a rubbery dummy head more than doubles the blockage of particles than when the dummy simulates coughing — aka spewing particles that can carry coronavirus — the study found. Notably, a surgical mask or cloth mask alone blocked 42 to 44 percent of the particles coming out of the cough doll, respectively. The combination of a cloth mask over a surgical mask blocked 92.5 percent of the high-risk particles.
Next, the CDC researchers gave the rubbery dummy head to an equally disembodied friend, about 2 meters away in a cozy, unventilated experimental room. When one of the heads quietly vomited aerosol particles (source) while maskless, the researchers measured the dose of particles the companion (recipient) absorbed over a 15-minute period. Wearing only a surgical mask reduces the recipient’s exposure to particles by just 7.5 percent, compared to wearing no mask. Wearing a double mask reduced exposure by 83 percent.
Then the researchers reversed the scenario by trying masks on the source and leaving the receiver maskless. A surgical mask alone on the source reduced the recipient’s exposure without a mask by about 41 percent. When the source wore a double mask, the maskless recipient’s exposure dropped to 82 percent.
When both the source and recipient wore dual masks, recipient exposure dropped to 96 percent.
Finally, the researchers also tested tucking and tying a surgical mask onto the receiver or source head. The pleat-and-button reduces side vents that allow unfiltered breath to escape. This alone reduced recipient exposure by 64.5 percent and 63 percent, respectively, when used by either the recipient or the source. When both heads put on masks and tied them up, exposure fell again by 96 percent.
Conclusions and Warnings
“These lab experiments emphasize the importance of a good fit to maximize overall mask performance,” the researchers concluded. The agency’s researchers also noted the potential benefits of using other mask tightening methods, such as using sheer nylon stockings around your mask or a mask-fitter product to help keep masks tighter around your face.
However, let’s make some important caveats. The researchers emphasize that they mainly looked at family member improvements in mask performance. The agency tested only one of each mask type (surgical and cloth) and one type of combination: cloth over surgical mask. There is a plethora of mask options and ways to combine them all. It’s also unclear how the double-mask method used in the study would compare to more rigorous mask designs, such as those from the World Health Organization. That’s not to say your specific results may vary. Finally, another obvious limitation is that the researchers used rubber cups, not the real one.
“The findings of these simulations should not be generalized to the effectiveness of all medical procedures [surgical] masks or cloth masks, nor interpreted as representative of the effectiveness of these masks when worn in the real world,” the researchers warn.
And, in the broader context of the threat of more contagious variants, it’s still unclear how much increasing your mask game will help. So far, the standard wearing of masks and the other usual protective measures – physical distancing, avoiding crowds and poorly ventilated indoor areas and good hand hygiene – appear to remain effective against the variants. Still, as many experts have said recently, it probably doesn’t hurt to improve the mask’s performance.