As a non-smoker I've had enough passive smoking induced bronchitis to last me a lifetime- that's the negative memory of folk clubs. Not that pipe smokers were any better. I remember singing one night when the Rev. Kenneth Loveless was the guest. He sat in the front row with his pipe polluting the air quite nicely. No idea what sort of shag he'd stuffed it with but it must have been industrial grade! I can't remember what I sang but I do know that at one point instead of air I got a lungful of smoke....heavy coughing fit....end of song.

@Andrez: early mornings are even worse! There's virtually no-one about but if someone has crossed the street 10 minutes earlier their smoke still hangs there.