... or so you think. Mold contamination is most of the times invisible and triggers long-term chronic intoxication. People only realise there's a problem if the mold starts growing on the walls, at which point it's too late.
It's funny that people born here don't know about it and I, an European buying a house and asking the workers that came for some initial renovations, found out. The wall guy said he often finds small amounts of mold when he's called to replace drywalls, but owners don't like to be told about it.