The trouble is so many heavy-duty cleaning products are horrible for humans who have to enter the place where they were used within the next hour, while leaving a certain number of insect species completely unfazed. A friend of mine, as a student, had an ant problem in his grotty one-room bedsit. As it was one-room, which he had to live and study in (plus he had limited funds), industrial antkiller was out of the question. So he put a heap of sugar by the door where they were coming in. The idea was that if a ready supply of sugar was available to the ants at their point of entry, they wouldn't bother trying to get into his cupboards, clothes or bed any more. It worked too. Except that the concentration of ants immediately around the door grew to the point where non-students wouldn't cross the crawling threshold... might be a bit impractical for an ambulance.