I've never heard of a cigarette smoke detector. Several years ago, I read an article in the NEW YORK TIMES about the management of an apartment building on the Upper West Side of Manhattan that wanted to restrict the building so that all new tenants would be non-smokers. It was hoped that, eventually, the building would be a smoke-free building. All current tenants who smoked would not have been affected. They could stay, but no new smokers would have been allowed in the building. Apparently, some smokers started protesting and began legal action even before the smoke-free proposal got off the ground. I don't remember the details, such as whether it was a co-op or a rental building. I vaguely remember one of the smokers saying that a smoke-free building would be discriminatory. Another claimed that he had a disability and, therefore, needed to smoke. I can't remember whether he thought his disability was the need to smoke or whether he had some other disability that forced him to stay at home all by his lonesome self with no pleasures in life except the "pleasure" of smoking -- or some such nonsense. Again, I don't have the details, but you can probably search for it in the archives.
Frankly, I would LOVE to see smoke-free apartment buildings. Although I am currently staying in a house, I have spent most of my adult life living in apartment buildings, and I am sick of being exposed to second-hand smoke. I hate the smell of cigarette smoke, and not a week goes by when we don't hear of the dangers of second-hand smoke in the news.
Perhaps, if your friend has a building smaller than eight or five units, he might have more leeway as far as what he can dictate. In some communities, tenants have more rights when the building has eight or more units. Does your friend intend to live in the building? If so, then perhaps he can tell prospective tenants that he or a family member has severe, life-threatening asthma or bronchitis and cannot be exposed to smoke.
I think stricter laws should be passed regarding non-smokers' rights. Granted, you can't tell a tenant what they can do in the privacy of their apartment (I think that has something to do with the tenant's right to the quiet enjoyment of the premises), but the problem with smoking is that it goes well beyond the privacy and confines of the apartment where it is occurring, and it DOES affect other tenants in other apartments. It affects the health of the other tenants and the peaceful enjoyment of THEIR apartments. Smoking also damages property. The odor of cigarette smoke can linger for YEARS. I bought a used textbook at Barnes and Noble about 15 years ago. The previous owner was a smoker and, to this day, the pages of that book still smell of smoke. They don't smell as bad as they did when I bought the book, but you can still tell that it was exposed to cigarette smoke.
I think your friend should definitely consult a lawyer to see how he can make his property smoke-free.