I used to go to a session, before the smoking ban, in a pub where lots of punters smoked. It was so bad that when I got home I'd have to throw all my clothes into the washing machine and have a shower before going to bed or I'd smell like an ashtray. The pub had a recirculating filter in the ceiling which did help quite a bit with breathability. But it emitted a shatteringly loud mains motor hum. An A flat drone as loud as a bagpipe is not a great addition to the Scottish dance tune repertoire.