I wasn't just thinking of hospitals. Our local education authority has been replacing old schools (with windows that open, so every classroom was independently ventilated) with big glass boxes sold as "community hubs" and funded by PFI (the Blair/Brown scam). My wife went to Pilates classes in one. The windowless room they got had NO air inlets at all - it just used whatever air flowed through the cracks from neighbouring rooms or in the door when you opened it. If you used it now you'd be inhaling viruses that had drifted the length of the building through at least two other rooms.