The object gets created for 15 seconds, I believe. It takes about 5 seconds to actually start producing the smoke particles, and they linger for about 10 seconds after the object is removed.
If the object is removed and 0.1 seconds later someone exits an interior, there won't be any more smoke being produced so they'll see no smoke but players that were outside will see smoke for around 10 seconds more. Not much I can do about that really.
