DON MCBETH comments on masks in his letter published on July 19. He says he does not suffocate when the mask is on. I'm glad for Don's sake.

But he deduces that ALL the air he breathes in and out is passing ONLY through gaps around the edges and therefore includes airborne virus particles. I

suggest a little experiment; take a clean tissue or piece of toilet paper and a similar sized piece of polythene. Hold the sheet tight to your lips with your mouth open and breathe in. Compare the two. Kleenex is permeable, polythene is not. And your glasses may still steam up!

Imagine the air full of mosquitos; breathing through a sieve would allow air in but keep flies out. All PPE (personal protective equipment) is designed to reduce risk, as are other measures such as social distancing. Like vaccination, no method is 100 per cent but we can reduce the risk of catching or spreading Covid-19 by adopting these control measures and understanding how they work.

Choose a face covering that fits well around your face (a metal nose bridge piece can be shaped to your nose in the NHS issued masks) and stays in place over mouth AND nose when you speak. The number of airborne droplets which have been breathed/sneezed out by other people (as well as diesel particulates and mosquitos) will be radically reduced by the filtration effect of your mask, so you breathe cleaner air.

The better the filter, the lower the risk. So an NHS-type medical-grade mask will do a better job than two layers of fine cotton but this will do better than a single layer, a piece of net curtain or a visor. The same applies to exhaled air; if you have asymptomatic Covid you are less likely to pass it on if your exhaled air is being filtered. The virus will mostly be trapped in your mask.

Don says that a recent study showed that influenza infections have fallen dramatically since the widespread introduction of face coverings and social

distancing. This is logical, based on similar methods of transmission to Covid, from person to person. A big difference is that the virus causing Covid-19 is far more transmissible than flu so it is much easier to catch Covid and it spreads much faster as a result. Don quotes a "95 per cent fall in influenza" and finds it hard to reconcile that with "25,000 Covid infection per day and rising". I'm not sure about his figures, but for me there is no dichotomy. If the fairly widespread adoption of masks and distancing have reduced the spread of flu, just think how overwhelming the Covid numbers would be if we stopped using those control measures. Stay safe!

Steve Waters