As the highly contagious Omicron variant continues to circulate, some people may be looking to PPE-grade face masks, such as FFP2 respirators, to protect themselves.
Travel to some foreign countries may also require them, as mask rules differ abroad.
These types of masks conform to specified standards and are made from synthetic, non-woven materials. They filter more than 94-95% (depending on the type) of tiny particles, and have a closer fit designed to protect the wearer.
Some scientists and doctors have also suggested this might be a sensible measure for some higher-risk scenarios, now that we have increased understanding of the importance of aerosol transmission.
However, you might have found that getting the correct mask isn't as straightforward as expected.
There are hundreds of shapes and variations available, with similar masks called different things and a high risk of fakes, particularly if buying online.
They're also pretty expensive, especially if you need to use them regularly. Most are classed as single-use, so can you get away with reusing one to save money (and the environment)?
We've got the lowdown on choosing masks, spotting fakes, and using (and reusing) them properly.
You might have seen medical or respirator masks called different things.
These names correspond to the performance standards they have to meet in the country they're manufactured or sold in: FFP2 in the UK and Europe, N95 in the US and Canada, and KN95 in China.
The safest bet in the UK is to go for an FFP2 mask, as you can be sure it will conform to relevant standards here. Masks manufactured to international standards may not be certified for use in the UK.
Unfortunately, there have been widespread reports during the pandemic of dodgy or counterfeit PPE being sold online, so you need to take care when buying.
What to look for:
Other positive signs are if the masks come in tamper-evident packaging, with manufacturer instructions and proof of certification.
Most pharmacies should stock them, as do many DIY stores - for example:
Even the best mask is no good if it doesn't fit your face well though, or you don't position it properly.
Despite higher filtration efficiency levels, if your mask doesn't fit well, it won't do the job.
The mask should fit snugly to your face, with no gaps, and you shouldn't be able to feel any air escape through the top or sides of the mask when you breathe out.
Bear in mind that this will be near-impossible to achieve if you have significant facial hair.
Not all FFPs have the same design, so you may find that one shape suits your face better than another.
Some have a fold down the middle of the front of the mask, others are more dome-shaped, and some have a horizontal panel across the front overlaid on a moulded dome.
Pay particular attention to how well the nose wire and ear or head straps secure the mask to your face - these aren't of the same quality or materials on all FFPs, and they can make a big difference to how well they fit.
If you'll be wearing it for extended periods, such as a long journey on public transport, you'll also want to ensure it feels comfortable.
We've previously warned against choosing a face mask with a valve, as this lets your unfiltered breath escape and won't adequately protect those around you.
These masks are designed for scenarios where that doesn't matter, such as working with hazardous materials or for DIY.
If you've accidentally bought a face mask with a valve, or it's your only option, you might be able to seal the valve from the inside with duct tape (this would still let you breathe through the rest of the mask and filter your exhalations). Make sure it's well sealed though.
FFPs are technically designated as single-use, or 'non-reusable' products (this is what the NR on the packet denotes).
But evidence is mounting to support the view that FFP masks can be reworn, as they may remain effective for longer periods of time.
This would greatly reduce the waste created by these products and help make them more accessible.
Claire Horwell, professor of geohealth at Durham University, was researching the effectiveness of face masks before most of us gave them any thought - studying the health hazards of airborne volcanic ash.
She says the idea that disposable masks should be thrown out after eight hours of use doesn't necessarily make sense in the context of everyday protective use by the public.
FFP2/N95 type masks were originally designed for healthcare and industrial workers who are exposed to high levels of hazardous particles over the course of a shift - but that this doesn't mirror everyday use by the public during Covid.
While it's still important to bear hygiene in mind with your mask, there is scope for reuse.
Mask manufacturer 3M recently issued advice for the public saying that 'respirators can be worn until they are dirty, damaged or difficult to breathe through.'
Professor Horwell suggests having a few masks on rotation, rather than simply reusing the same mask over and over. This allows you to air them out in between uses.
She advises that masks should be left somewhere clean and dry to air for a few days in between uses, which should mean that any viral particles attached to the mask become less of a risk over time.
You shouldn't machine-wash, bleach or tumble-dry disposable masks, as this can damage the electrostatic charge in the mask's layers that contributes to the high filtration level.
A found that you may be able to hand-wash some disposable masks in warm water, or soak them in boiling water, while retaining their filtration abilities - and a test by French consumer organisation Que Choisir found similar results.
However, both studies were done on blue surgical masks, which are slightly different.
Of course, there's more research that needs to be done about just how long masks may retain their filtration efficiency, and the possibility for contamination with repeated use.
There's some concern that the electrostatic layer within disposable masks could degrade over time, and that bacteria could be present on the mask, depending on use and storage.
Safe reuse is also contingent on the mask being handled correctly: not shoved into the bottom of a bag, picked up off the floor or prised from the mouth of an unruly pet.
Masks that are visibly dirty, stretched, damp, torn or worn away should be disposed of.