Our Nanny State Would Like to Remind Us: Smoking Only 1) at the curb, or 2) if no curb, At least 15 ft. from exits, entrances, operable windows, & vents.
You should also eat all your vegetables, chew with your mouth closed, brush your teeth, and stop slouching already. Did you write a thank-you note to Aunt Edna for those nice socks? Good. Now finish your homework and get to bed at a reasonable time.
We would like to add that, while slowly poisoning yourself it's a good idea to remain 15 ft (4.572 m) away from open buckets of gasoline or similar fuels. It would also be best to avoid mummies, the Scarecrow of Oz, Frankenstein's Monster, and other flammable film icons.
Of course the above admonitions apply to tobacco as well as anything else you might be smoking nudge, nudge, wink, wink. The lighting of incense is also heavily discouraged. We cannot legally forbid the application of way too much perfume/cologne but... you know how there are always people making gagging noises around you, like in elevators and in line at the bank and theater? It ain't a coincidence.
Ok then! SFist personally used to love our opposite commute to Berkeley on BART in the morning when the handful of us left behind on a previously crowded car at Montgomery Station would all simultaneously start sneezing, thanks to the collective cloud of perfume and cologne that was left behind.