Something I've learnt as a newbie that I didn't find out during pretty extensive research... or maybe just common sense that I missed out on... not all household plastics are inert, and some will really upset animals.
I decided to replace the rather manky and cracked bamboo bridge/ramp that helped my small BP get up onto basking table/hot-hide in her tall viv. I found this lid of a cheap black plastic tub. I washed it and sanded down some sharp edges. I installed it in the morning and she immediately started roaming around. By the evening she was rubbing her face on it, and still didn't settle - she trashed her enclosure like she never has before and was jamming her nose in the gap between the sliding glass doors. I opened the doors and she leapt out into my hands.
Sniffing it up close revealed that it smelt a slightly "plasticy". Warming it slightly more with a hair-dryer made a strong chemical smell. There is no marks on it to say exactly what sort of plastic it is, but the bottom line is that my BP really hates it, and I doubt it was healthy. I removed the ramp entirely - she's now big enough to get onto the table without one. She's now settled down and has since eaten so I think she's OK.
At the very least, plastic items need to be heated and sniffed before put into enclosures... I guess the safest policy would be to only use items intended for animal housing.