No, A well-made scented cnadle - like an unscented candle - produces harmless water vapor and carbon dioxide when burned. The only difference with a scented candle is that a fragrance is released as well. Reputable candle manufacturers carefully monitor the additon of fragrance to ensure a clean and proper burn. There is a maximum amount of fragrance that can be added to a candle before it will no longer burn cleanly or properly.