The mantra “wear your mask” could soon be “wear your masks” as experts say two can be better in high-risk situations.
While healthcare workers often wear more than one – also so they don’t have to touch their faces to change them – some are encouraging the public to layer up.
Even Anthony Fauci, chief medical adviser to US President Joe Biden, said wearing two masks could help slow transmission of the coronavirus.
Dr Fauci himself often doubles up, as has Mr Biden in the past.
"If you have a physical covering with one layer and you put another layer on it, it just makes common sense that it likely would be more effective," Dr Fauci told CNBC's Today show in the US.
Countries around the world are grappling with more infectious variants of the virus. Governments have introduced new lockdowns and travel restrictions to limit their spread. Vaccines have brought hope the pandemic could be ending but mask-wearing will still be vital for the foreseeable future because it is not clear whether inoculation prevents transmission.
Experts have also cautioned that masks limit the spread of infection rather than protecting the wearer from catching the virus.
Dr Ponnusamy Tamilvendan, specialist for internal medicine at Medeor Hospital in Dubai, said the answer to the question over how many to wear depends on the type.
An N95 mask, which refers to a US standard that blocks 95 per cent of particles, is believed to be the best.
Another option is a surgical mask, which is made from three layers, followed next by cloth masks, which are the least efficient at filtering virus particles.
“If you wear an N95 mask, I don’t think anything more is needed,” said Dr Tamilvendan.
“But if you are wearing something flimsy like a cloth mask, adding another offers better protection.
“Surgical masks don’t offer full protection. So you can wear two if you are exposed to very contaminated areas. But if you are wearing an N95, that is enough, even in contaminated areas.”
Dr Shreehari Pillai, medical administrator and specialist in internal medicine at NMC Specialty Hospital, Abu Dhabi, said two masks are sometimes necessary in countries such as the US, where people tend to use cloth masks.
“What we use here is the surgical masks. Surgical masks already have three layers inside and they are medical grade. A single surgical mask is good enough,” he said.
“Otherwise there is no superiority, because the outer layer of the mask is usually waterproof. And if you put a cloth mask on top of it, it can interfere with it.”
It can, however, be hard to know whether a mask in the UAE is medical grade, as many of them have patterns, rather than the standard surgical blue colour.
“It should be indicated on the packet. Preferably, if you buy it from the pharmacy it should be medical,” said Dr Pillai.
Experts have consistently said mask wearing was only effective along with distancing and handwashing. Analysis from the US also outlined the benefits of “double-masking”. Its authors included Linsey Marr, a virus transmission expert at Virginia Tech.
The report said for maximum protection, members of the public can either wear a cloth mask tightly on top of a surgical mask or wear a three-layer mask “with outer layers consisting of a flexible, tightly woven fabric that can conform well to the face and a middle layer consisting of a nonwoven high-efficiency filter material (eg, vacuum bag material)”.
“If the masks fit well, these combinations should produce an overall efficiency of >90 per cent for particles 1mm and larger, which corresponds to the size of respiratory aerosols that we think are most important in mediating transmission of Covid-19,” the analysis said.
Dr Tamilvendan said if there is any uncertainty, there is no harm in doubling up.
“If you are not sure about the quality, then use two masks,” he said.