I suppose they might have burned sulfur to fumigate a room in the distant past, but there are a lot better disinfectants. Washing things down with bleach then closing the room so the hypochloric acid vapors build up should wipe out just about all life in the room. Setting up an ozone generator and closing the room would also do a great job.
But, in any case, when finished they should open the windows and use a good sized fan to suck all the stuff out so there would be no smell left. Sounds like the people in your hospitals are too busy, too lazy, or too uninformed to do all that, Mriana.
I’m sure Asanta and Macgyver can shed much more expert light on this.
Bleach doesn’t kill everything. Cryptosporidium, for example, is immune to bleach. There are other diseases as well, which can’t be killed by it. I think hepatitis might be one.
And again, you have to worry about the pathogens building up a resistance to whatever cleaning agent you’re using. High heat is probably the best thing, but its a little difficult to stick a whole building in an autoclave. So the next best thing would be to rotate the cleaning agents.