Firefighters (there ARE a few women in the profession now) definitely meet a lot of hotness criteria - or at least automatically have the potential to - in my book. To begin with, they have to be in excellent physical condition. The possibility always exists that they'll need to haul/control a hose filled with water or carry an unconscious 300-lb person down a ladder (worse yet, one who's freaking out 'cause their home is in flames.)
More important than that, in my experience firefighters' personalities fit squarely into one of two categories: nerd or "average Joe." Why ask why, but there's a subset of geeky boys who have always been attracted to this line of work. (Maybe it's superhero wish fulfillment to spray foam on gasoline/oil spilled in a car accident and save the vehicles from catching fire?) Then in the other category you have the kind of guys who were having too much fun in school to apply themselves to academics very much but still wanted to have a productive and satisfying existence. In their teens they may or may not have been jocks, but they would've definitely socialized mainly with their male friends. In adulthood they still prefer the company of men. Whether they're 15 or 50, give them a deck of cards - or a TV with whatever game on - along with a few buddies, and they're good to go. Fire stations could just as well be dorms or frat houses with all the pranks and horsing around that go on. It's a man's man's life. Then when the alarm bells sound and the scanner squawks it's time to go to work - with one of the highest risks of any occupation that not everyone will finish the job uninjured or even alive. For all the clowning around the "jakes" do between calls, when they're needed they don't play.
Few real firemen look like models, true. But they're typically either tall taut n' wiry (the nerd category) or barrel-chested and stocky (the average-Joe category.) Either body type is A-OK by me.
So is the down-to-earth and unselfish nature of most of 'em.