Questions about Smoke Detectors

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Questions about Wiring Smoke Detectors

Question from Mike, an Electrician from Patchogue, New York:

Can the carbon monoxide alarm be connected to the smoke detectors in series and be the last on the line? I haven’t been on the job for a few years and I just want to make sure that is how it is done again. I know the smoke detectors are in series, but I forget if the carbon monoxide can be connected to it as well.

Dave’s Answer:

Many local areas require permanently installed carbon monoxide detectors with battery backup which are used to detect odorless gas which could be fatal. Check with your local building jurisdiction for the specific requirements, and if combining the circuit wiring of carbon monoxide detectors and smoke detectors is permitted.
Citation Reference: NEC NFPA 72 Article Section 29.5

Question from Mike, a Homeowner from Twin Falls, Idaho:

I want to install smoke alarms. Can I use 14/3 wire or do I have to use 12/3?

Dave’s Answer:

Smoke alarms may be wired from a circuit using 14/3 wire.