I worked in hospital operating theatres and other departments nearly 50 years ago: we all wore masks: surgeons, anaesthetists, nurses, theatre assistants, porters: no-one, but nobody at all was exempt. You just got used to it, wearing them all day, with maybe a new one after lunch if you got a break at all. So I am slightly sceptical of some modern-day claims to be exempted from wearing masks now: e.g. whole gangs of teenagers going into the local Co-op for their lunchtime fast food fix, ALL claiming they can’t wear masks as they have asthma!