Is it unsafe....

[Frodo]

Originally Posted by Timco

It's physically impossible to ignite gas or gas vapor with a lit cigarette as I understand it.

I agree with this. Years ago (back when I smoked), out of curiosity I once tried to see if I could get a little gasoline I had dribbled onto the driveway to ignite with a lit cigarette. It was seemingly impossible---ultimately I ended up crushing out the lit cigarette in the middle of the small puddle, with no flames resulting.

That said, I'd still not pump gas with a lit cigarette in my hand or mouth...if for no other reason than it would make one look like an complete fool!