Back in the 80s I lived in an Army married quarter. We had dogs and issues with fleas. The houses were on short stilts and the dogs could get under them. The Vet sold us some concentrated chemical in a can. It was diluted with water and sprayed around and under the house. The instructions were very clear. You couldn't use it inside a house. It worked very well but we had to respray every other year.
Looking back now I hate to think what was actually in that chemical.
