Do I need an N95 mask and if so, can I re-use it?

Firstly, air dry your mask in the sun after use in order to disinfect it, says Bennett, who advises buying multiple masks so they can be rotated while each is being cleaned, and then throwing each out after it has been worn “a few times”. She recommends leaving a couple of days between wearing the same mask again.

There’s “no magic [amount of] time” the mask needs to stay in the sun. “Just give it a good dose of sunlight when you take it off… They work better when they’re absolutely dry. Don’t spray it with anything, don’t moisten it, don’t use disinfectant.”

Dispose of your mask if it gets wet

Don’t re-use a mask, adds Sim, if it is exposed to the rain, and don’t put it in your pocket between wears. Ideally, you would put the mask in a plastic, zip lock bag or a box with a lid (to ensure it won’t be crushed), and do so only once the mask is completely dry. “It’s going to damage the integrity of the seal,” he says, of a mask that is placed in a pocket or handbag. “Because it will be crumpled. It will open up gaps, and the protection drops off pretty quickly in those circumstances.”

Fit the mask to your face – ‘almost vacuum tight’

People need to manage their face carefully, too, before they wear the mask each time: the presence of any facial hair or oils on the skin can damage the mask’s seal, as can skin irritations that cause inflammation, he adds.

But perhaps most importantly, say experts, the mask needs to continue to fit tightly over your face, without any gaps along the edges or around the nose.

“If you’re not particularly checking its fit, you’re probably wasting your time,” says Bennett, adding that when hospital staff wear N95s, their masks are “fit-tested” by a specialty machine to make sure they’re “almost vacuum tight”. “If you’re drawing in air around the edges of the mask or expelling air around the edges, they’re not working to that [designed] specification.” (When used properly, respirator masks filter at least 94 per cent of airborne particles at a size of 0.1 microns.) “That specification is [based] on all air going through the mask [rather than out the sides].

“I’ve seen people wearing them out in the community, they pull them on and off, have stretched the ear loops, they’re hanging loose on the face,” she says. “They’ve probably got a false sense of security. They’re probably not a lot different from a surgical mask.”

Avoid handling your mask

It’s crucial to handle the mask as little as possible, wash your hands after touching it and ideally take it on and off using the ear loops. Bennett says an N95 is not a good choice for a mask you plan on putting on to go into a café or shop, and then taking it off once you nibble on something, and then put it back on afterwards, and so forth.

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“You might get infected [with the virus],” she says, as COVID particles may be present on the outside of the mask. “If you’re handling it from the outside, that’s why they say to put it in a [plastic] bag [when you carry it with you], because if you have the virus on your hands, there is a small risk that you could have your hand to your face, rub your eye, and that might be all it takes to get an infecting dose.”

“Ideally, these are the masks that people pull out on special occasions,” she adds of respirators, like those who are visiting people who are vulnerable to infection, going to a neighbourhood with a high-infection rate, or travelling on public transport when it’s packed with people. (They’re also good, she says, for those who have “a very people-facing job”.) This is why Bennett, who is rarely in these situations, usually opts for a disposal surgical mask – used once – under a close-fitting three-ply cloth mask. “That’s probably the next best thing to do after an N95.”

Professor Bruce Thompson, dean of health sciences at Swinburne University, agrees, and is firmly against re-using an N95. “Ultimately, you’ve got to assume that the thing’s got infected once you’ve used it,” he says. “That’s the whole reason you’re using it, to not contract the bug. You [should] treat them like your [already worn] underwear. Don’t touch them or share them or reuse them.”

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