Experts are now recommending wearing a surgical mask and cloth mask together for better protection against coronavirus. The recommendation comes at a time when more transmissible variants of COVID-19 are being discovered across the world. Experts are also saying that it is now time to consider wearing a medical-grade respirator, which people were not able to access during the start of the pandemic due to short supply and needs of frontline healthcare workers.
Scientists agree that the coronavirus mainly spreads through the air in the form of small droplets let out while breathing or speaking. These droplets can travel many metres and are a common mode of virus transmission. Masks have been the primary protection from these droplets.
Linsey Marr, a professor of civil and environmental engineering at Virginia Tech who studies airborne disease transmission, told news agency AFP, "How well a mask works depends on two things: filtration and fit."
"Good filtration removes as many particles as possible, and a good fit means that there are no leaks around the sides of your mask, where air -- and viruses -- can leak through," she added. She stated that even a small gap could reduce mask efficiency by 50 per cent.
Marr explained that the best materials for blocking small particles are non-woven polypropylene, which is used to make N95s and the HEPA filters in planes. Tightly woven cotton is the best fabric for blocking droplets.
"If you wear a cloth mask, choose one that has multiple layers, ideally one with a pocket that you can slip a good filter material into," said Marr. "Or you can double mask by wearing a surgical-type mask with a tight-fitting cloth mask over it."
Surgical masks though good at filtering things out are loose. So adding a cloth mask on top of the surgical mask holds down the edges and reduces leaks. Adding another layer of protection also increases filtration.
Marr added: "We do not recommend wearing more than two masks. Adding more layers proves diminishing returns and can compromise breathability. It must remain easy to breathe through the layers; otherwise, air is more likely to leak in around the sides of the mask".