Replacements for candles and incense to represent fire?

I've been living with my sister for awhile and will be living with her long term, but there is a small problem. She is very, very, very allergic to smoke to the extent that even candles and incense will give her a rash and a scratchy throat. Because of this, I do not intend to use any smoke-producing things in my craft or altar for the foreseeable future. However, I'm at a bit of a loss as to what to represent fire with. I usually try to incorporate all the elements as best I can, but in this case a se fire is a bit tricky. Any advice?