we have wall plug ins all over the house, a scentsy tray in the family room, and lit candles all the time all over the house. I dont think airborne stuff like the particles that make up the scent of the candle will do anything to our lizards, but too much smoke or larger particles like that will defiantly hurt any any animal. I also have a fan blowing about my chameleon, so its not like there is a candle 3 feet away poring in thick scent. that might get confusing for the lizard. Just my 2 cents.
Of course! I know that you get paranoid with these chameleons, But a candle will be fine, The only possible downside would be the wax dripping catching something on fire, then your house burning down.... but ya....
All else being appropriate such as good ventilation and RH I can't imagine a candle causing any major issues. My wife insists on incense in the room next to the Chameleon and I haven' noticed anything other than snow white urates.
I would personally not use candles, incense, smoke, cooking, or anything around my chameleon given a choice but I doubt major harm (or likely even minor harm) would result from doing any of these things in a well ventilated room.