I would definitely not put anything with any chemicals inside the tank that does not have a known reptile logo on it, e.g. Zilla, ZooMed, etc. An alternative would be to burn a candle perhaps or even get some incense, but put it away from the cage so the smoke doesn't go near the dragon. Smoke is very bad for any animal, even humans, so stick it somewhere where it's ventilated--but since you're in a small room this may be a chore. I would say get some plug-in air fresheners and try them in your room and just see if it helps the problem.