one of my best mates's DH is a fire fighter, I asked her one day if she worried about him and she said surprisingly not, because it is his job, and he knows what to do and how to do it. but he doesn't get called to bush fires, he works at the airport.
I'm not sure how you would not worry, I think I still would. but he knows what he is doing, they go through so much training, over and over again.