People will need to wear a face covering in shopping centres, banks, takeaway outlets, sandwich shops and supermarkets under new regulations that have come into force in England.
Every member of the public will now have to wear a covering to avoid a £100 fine - whether it's made at home, disposable or a reusable cloth mask.
Face coverings should be reusable and can be made from materials in your home - such as a scarf according to guidance. You just need to make sure you have enough fabric to cover from the top of your nose to the bottom of your chin.
The WHO recommends a triple-layered mask, with research showing the best have an inner absorbent layer, such as cotton.
But if you're buying one online or on the high street, experts say you should be careful about being "ripped off".
It comes after retail giant Boots was accused of selling face masks at a 500% markup.
Biochemist and founder of MasksrUs, Antony Arulanandam said he is concerned consumers are being overcharged and sold poorly made face coverings.
"When shopping for a face mask, look on the label to see if it has achieved a score of more than 99% under standard Bacterial Filtration Efficiency (BFE) testing, also known as ASTM F2101-19," Arulanandam explained.
"These will provide the best protection. In fact, that’s the score masks must meet to be worn by surgeons in operating theatres."
He said shoppers should not dwell on price, adding that a good, reliable mask should "not cost the earth".
"A good mask doesn’t have to cost the Earth. Masks that meet this standard should be widely available for £10 or less and you should be able to make savings on multi-buys for families."
Reusable masks should be washed every day but very cheap masks will be less capable of standing up to being washed daily and won’t last, he added.
Arulanandam advises washing your mask at 92 degrees to kill coronavirus germs, and to look out for masks that are designed to be washed at this temperature.
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"Masks should not be washed with other items of clothing but washed separately," he added.
"The construction of face masks and the materials they use are also crucially important. Masks that are not single-use, disposable medical masks should be made up of more than one layer and not be 100% cotton.
"Though cotton is comfortable on the face, its fibres are too widely woven to provide an effective barrier. The best masks will have a tight polyester weave in the outer layer, often mixed with Spandex, Lycra or elastane for elasticity, with a blended-cotton weave on the inside."
Lastly, Arulanandam said customers should aim for one that "fits snugly" on your face without feeling too tight.
“When you wear a face mask, it shouldn’t be too loose or too tight. It needs to be comfortable enough to wear for long periods but shouldn’t leave gaps for the smallest aerosol particles to sneak in and out.
"It’s human nature to remove a mask to sneeze and, for some, it will take some practice to resist this temptation, as it’s a reflex action. If a mask is uncomfortably tight, people will be more likely to want to remove it when sneezing or coughing. It should fit snugly on your face and cover both your mouth and nose," he concluded.
