I might be a little naive, but I suspect that getting fired from BK for smoking a cigarette isn't going to be a deal breaker.

The Batlord has always been a champion for self improvement

But it was IN THE KITCHEN

It was at the back window which is at the end of a corridor well away from the kitchen. Most of the time nobody even noticed.

I sometimes interview / hire.

I would assume it wasn't the smoking in itself, but rather how one acted in an ensuing conflict after being confronted about smoking. That's not good.

If it comes up, SGR's suggestion to own up to it seems best to me. At least it indicates growth and might somewhat abate fears that something similar will happen again in a new job.

Yeah, not good.

But still, depending on the job, I don't think it would be a dealbreaker necessarily, especially if you explain it and frame it in a way that makes you sympathetic. Morale at BK was terrible, management didn't listen to employees, Batlord's second cousin (who he was very close to) died unexpectedly, etc. They need to believe it won't happen again though.

Or I can just not bring it up and say the air conditioning was becoming unbearable and I was already ready for a change anyway or something.

I thought the question though was "Why were you fired?" - or do they not know you were fired and they're just asking why your employment with BK ended? Just keep in mind, they could end up calling BK as a reference if you put them on your resume.

BK's on the application (maybe, not all the applications I sent out even had spots for work experience) but I didn't say I was fired.

No need to bring up the fact you were fired. Depending on the rest of your resume, they might not even call BK. Pretty sure HR is supposed to just confirm you worked there and call it a day, it's not like they have a long conversation about it. I don't think they're even allowed to? Idk I hate HR. Best of luck with the interview.

Relevant to my 'your day' post, actually. Between yesterday & today I got a promotion, a 15% raise (had another 10% raise just 6 months ago), hiring an underling, and mutual understanding with the president that I want to be working from home within 5 years.

I am celebrating with a drink right now. Very excited for the future.