I've said before that life is a series of learning opportunities, and who we are is defined by how we react and learn. Some people, unfortunately, either choose not to learn or are too stupid to realise a learning opportunity when they see it.
An older gentleman came to my trauma bay having suffered severe burns to his face and neck. Now burn victims have a rather unique odor about them (much like cooking beef or pork have distinctive smells...disgusting analogy, I know), but this guy smelled more like cigarette smoke. Plus, the distribution of his burns was a little strange.
It turns out that he had severe emphysema from smoking and was on home oxygen, but he just continued smoking...while the oxygen was flowing. Free flowing oxygen plus ignition source (lit cigarette) plus fuel (facial hair) = big boom.
While I'm on the subject of burns, another older lady came in having sustained third degree burns to her shoulder. She admitted to falling asleep while smoking, and the lit cigarette set her blanket on fire. When I examined her shoulder, the burned area seemed to have a strange checkerboard appearance to it, which I thought may have been transferred from the blanket.
Said the lady, "Oh, that's a skin graft from the last time this happened."