The risk of airborne transmission increases when occupants in a space are participating in energetic activity, such as exercising, shouting, singing or talking loudly. Safety campaigners point out that official UK and international bodies were slow to recognise the risk of airborne transmission. TUC advice, issued in January 2021, makes clear that: “The main way the virus spreads is airborne transmission — i.e. breathing in the air of an infected person.”