Oddly enough, firefighters, when they exit a smoke filled area, often light up a cigarette as soon as they catch their breath. I noticed this when I used to fight forest fires, and I've noticed it when watching my husband, who is a structural firefighter. Even people who don't normally smoke will ask the smokers for a cigarette. I've felt the urge myself, after emerging from a particularly smoky area on a wildland fire. Is it a physiological response? Does our body make us crave the smoke so the carbon dioxide levels decrease slower in our blood? Is it a response to the stress inherent in firefighting? I'm not sure, but I do know that the urge to smoke by firefighters after leaving smoke filled areas is real, and quite odd.