All very excellent points, and exactly the sort of things that people should be asking about with proposals like this.
Really I was just responding to the earlier Anonymous Coward who said: "Are all of you finished making up problems? When was the last time people suffocated because the oxygen level in skyscrapers without openable windows got too low? What, they actually live in there? Blimey! They must be using magic to ensure a constant supply of fresh air!"
Clearly there ARE problems to be considered. Perhaps they are all easily mitigated or aren't serious problems but it's not absurd for people to ask questions about them.