I don't see how only smelling a place where people have been smoking will cause bronchitis unless you are allergic to the smell. I don't know of anyone is but that's the only way I can think of that it would cause bronchitis. I would think that the cold had more to do with it than old smoke

perhaps this is it??? Here is a link that might be useful: smoke signals

There is a standard. A number of them actually, they just don't apply to proprietary residential smoke detectors. There's a 4-wire standard, for 24V-powered smoke detectors with a set of contacts to report to a central controller that smoke is detected. There is a 3-wire variant, which shares one of the contact terminals with one of the power terminals. There are newer digital serial standards. If I want to turn this guy's house into an office building, school, or factory, then there are definitely standards available. Unfortunately, they require him to buy stuff, something he seems very... uhh... well, did I mention I told him to buy a set of matching smoke detectors and he came back with only two, which don't match either the existing units or themselves??? It appears from my searching the internet that Firex (existing) simply connects the 9VDC supply to the interconnect wire to signal, and both of the new ones are Kidde, which is apparently the same company - whose website seems to indicate they are compatible... At this point, I'll believe it when I see it. Work resumes Monday.

Sue, I don't know your son's circumstances but I do know how hard it can be to Stop smoking. One of the best pieces of advice I've ever heard was "A setback/relapse/failure is just one more step on the ladder to success, keep trying and eventually you will succeed" I stopped smoking almost 7 months ago after smoking a large pack every day for 43 years (maybe not soooo much in the first 10 years). I'm so enjoying the freedom from being a slave to cigarettes. Good luck to him.