I can't imagine what is causing the odor. I keep 8 snakes in my reptile room and never have any odor whatsoever. I check their tubs every morning and every night - if any of them have any urine or poop I immediately clean their tub. No smells ever linger in the snakeroom.

I use Aspen in some tubs and kraft paper in others.

Maybe the smell is coming from somewhere else other than the snake cage.

Good luck with solving this mystery.