I used to work in a fairly large holiday resort. We used to 'fog' accommodation when someone had been unwell during their stay, usually with symptoms of Norovirus or similar. As mentioned before, they are fairly well used on cruise ships and have been for quite some time. I never knew too much about them, other than we stuck a cap over the smoke detector and they filled the room. We let it settle for 24 hours and came back to find a fine layer over every surface, which could then be cleaned off and surfaces buffed and polished back to normal. It was a lot of work for just a few rooms, and had quite a distinctive clinical smell. I have no idea how effective this would be in such a large indoor area, I guess it would take some doing to guarantee every surface was covered, and I can't imagine very cheap either....