In the town I am a firefighter in they are building a new apartment complex where they are using combination interconnected smoke/CO detectors. Usually if it is a smoke alarm there will be some sort of indicator on the head that was activated and CO alarms normally have an alarm indicator, and both work well as long as the homeowner doesn't reset them. It can be more of a bother to the homeowner if they reset because if we don't smell any smoke and there are no readings on our CO detector then they have to wait and see if they have a faulty head. About 80% of our CO alarm calls are just for low battery, they must think the single chirp every 5 minutes or so is an alarm.
