But Dr Hughes - who has become known as "Dr Fresh Air" for his campaigning on the issue - believes it should say
"hands, space, face, replace.
He says replacing stale air in a room with fresh air from outside can massively reduce the chances of people becoming infected.
Dr Fitzgerald says it is not about throwing every window open wide all day, but making sure there's enough of a crack to let in fresh air.
And the answer is to add another layer.
"I'd recommend wearing a woolly jumper rather than just a short-sleeved top.
"But that's what we should be doing anyway, to save on heating bills and reduce our energy demand as we all do our bit to tackle climate change."
Dr Hughes says airing rooms for a few minutes several times a day won't lose much heat but will keep people safer.
And his idea for a Christmas gift? Thermal underwear.