What I know as fireweed, tall plant with pink flowers , turning to fluffy seeds, has, as far as I know two uses, there may be more, but the young shoots I think, if memory serves me right can be eaten, but I'm not 100% sure on that. I can't find my book to check, so someone may put me right on that.
The fluffy seeds can be used as tinder in a tinder bundle. They take a spark easily, but, like old man's beard, are a flash tinder with a short burn time. I put them inside my tinder bundle and the charcloth on top of that to help establish a flame. Or use them with a fire steel, in the same way, with other tinder that burns for longer.