Haha, here's a good one I'm going to use next time I get the "you can't do that, I have asthma" line.
"So do I."
On a separate note, I was once asked to put out a cigarette because I was walking by a building with a gas leak. I asked the technician, "So is there a 5 ton
tank in there?" He turned his head to the side curiously. "Because that's how many parts per million it would take to saturate the air 200 feet from the leak. And it would all have to leak simultaneously." He huffed and said, "well could you just not let anyone see you smoking."