If you have the interior done, yes, it can harm your snakes, slowly, but surely it builds up. The chemicals used are neurotoxins, until recently, there were warnings on some of the labels about not using them around birds and reptiles. I work in Pest Control, there is no way I would use the chemicals around my critters.
External treatments 'should' be ok (not ok for wild critters of course), as long as you keep your critters away. I still wouldn't do it. *shrug*