It depends...generally, closed oil heaters are safest for brids (outside of standard furnaces etc). Burning ANYTHING can harm them, but it just depends--- fat/grease/fry heated at high temps (even if not burned) can kill them, ptfe/pfe/pfoa/pfcs can kill them, cleaners, oils, scents, candles, vapes, wax melters etc---- they are just SO sensitive that I wouldn't use a fireplace with mine around (gas or wood).