WHEN WEARING TWO MASKS MAY BE BETTER THAN ONE...

COULD wearing two masks instead of one be the best way to protect yourself?

The idea of double-masking is based on the theory that building up multiple layers of filters will further reduce the chance of tiny coronavirus particles infecting you or others. It might also compensate for any inadequacies of the other mask, such as looseness.

Numerous studies have now shown that face masks can reduce the transmission of Covid.

In the journal Proceedings of the National Academy of Sciences in December, researchers found that in the 20 days after masks became mandatory in Germany, the number of new infections fell by 45 per cent. Now a U.S. report in the journal Med suggests that one option for maximum protection is wearing two masks.

The researchers reviewed existing evidence on different types of face coverings. For basic protection, they recommended a ‘high-quality surgical mask or a fabric mask of at least two layers with a high thread count’.

But another option was double masking — wearing a cloth mask ‘tightly on top of a surgical mask’, they said; the surgical mask acts as a filter and the cloth mask provides an additional layer of filtration while improving the fit.

An effective alternative is a single, ‘three-layer mask’ (with the outer layers consisting of a flexible, tightly woven fabric that moulds to the face, and the middle layer a high-efficiency filter, such as vacuum bag material).

Both options, if well fitting, should prevent more than 90 per cent of aerosols from getting through, concluded the review by the University of California. (By comparison, a study in the journal mSphere in October found a cotton mask is 20 to 40 per cent effective; the goldstandard N95 mask prevented 80 to 90 per cent of virus particles).

While in theory double-masking makes sense, a better option is simply a properly fitting mask, says Dr Andrew

Preston, a reader in microbial pathogenesis at the University of Bath.

‘A face mask should have more than one layer to provide the filtration required without making breathing too uncomfortable,’ he says.

‘Fit is important: poorly fitting masks will expel our breath through gaps.’

Tweaks to enhance a mask’s fit include ties that secure the fabric around the back of the head — relying on ear loops allows masks to hang and gape — and choosing one with a nose bridge. ‘Rather than hoping two poor masks will work, focus on using a multi-layered single mask that fits properly,’ says Dr Preston.