So I have been wondering this for about a year and a half. Working at a factory that customizes to what the customer wants we get some pretty weird requests but this one puzzles me. Why do they have us putting smoke detectors in 100% OSA package RTU's? These are units without returns mind you. Exhaust is being handled by other units. Most of the time they seem to be headed for NYC but not always. I have not been able to get a real answer for this, standing answer seems to be detecting fires in nearby buildings or forest fires.