Definitely do NOT throw a still smoldering butt into a garbage can. Fires happen like this:
When I was in high school, we were allowed to smoke on school property, but only at the "smoking doors." Those doors were located miles away from any class except gym (and ironically, right next to an air intake vent) so when one wanted to grab a quick puff between classes, we would nip out the closer doors and hope to not be seen by a teacher. The teachers seemed to mostly overlook this. One day, just as the bell was ringing, a teacher came out. I was at that point the only person with a still lit cigarette.
"Put that out right now!" he yells.
So, I bend down to put it out on the (non-flammable) concrete steps, 'cause classy chick that I am, I wanted to save the other half for my next break.
"Don't throw it on the ground!" he says.
No problem, I was planning to put it out, then trash it. "Just a second I say."
But, I'm too slow for Mr. Powertrip. So, I'm trying to put the cigarette out, while sputtering, "but but, I'm just..."
"In the garbage now, or you'll be explaining this to the prinicpal!"
So, I did exactly as I was told. I put the cigarette butt in the garbage. And about 30 minutes later, the fire alarm went off. And I never heard anything more about it, but I've always wondered if Mr. Powertrip made the connection between my cigarette and the (small) fire.
So, please, please remember to put that cigarette out, before throwing it out!