Years ago on an automotive forum we were discussing this topic. Someone suggested that you might want to avoid open flame heating sources if you're planning on working with things that tend to get explodey, like gasoline vapors--and if you have one and you're generating fine sawdust, you probably ought to invest in a dust collection system.
Can't say I've ever worked in a heated garage, so I've never tested that theory.
I had a classmate burn to death when I was in 6th, 7th grade -- best the fire chief could figure, he had a lit cigarette in his hand while he was pouring gasoline into a lawn mower. It was awful.