If you look at the label on the bottle of the fo, it usually states that it is for use in candles, gel, etc. and will also note if it is skin safe or not. I don't think you have anything to worry about, especially since you're only making tarts and wickless candles. I don't know exactly what type of fo would be considered not safe to use...perhaps an actual perfume? All I know is that you can use any fo that is candle safe and skin safe in wax. However, you can't use an fo that is made for candles in B&B, unless it says specifically that it is also skin safe. As far as gel is concerned, there are some fo's that will work for gel and some that don't. If you buy from a supplier, they will state whether it's good for gel or not. When your buying on the classy's, you should still have the labels attached to the bottles of fo's, unless the seller re-bottled them...then you'll never know for sure. If you're using the recommended amount of fo in your wax applications and using a standard warmer, you should have no problems exceeding the flash point.