Question:
Our new home has standard smoke detector installed in each upstairs bedroom, plus two locations downstairs, and one in the basement. These are the 120VAC type that use house wiring for power with battery backup, and emit a siren when activated.

I want a solution that will interface with my Caddx Security/HomeVision Automation system. I would want to replace the ones I have with the same type, but that have the additional functionality of a dry-contact for alarm notification to the Caddx System. I would also like to include CO2 detection in at least a few of them, as we have gas appliances, heat and fireplaces.

Firstly, does such a unit exists that is powered by 120VAC with battery backup, has contacts for external alarming and has built in CO2 detection?

Secondly, are there any Fire regulations or insurance regulations that I have to be aware of when changing out the detectors that came with the house?

Answer: In a word, no. There are no combined detectors that do all of that. There are some 110VAC/9VDC detectors that have a separate output which can be connected to an alarm. The few that I've run across used a separate relay module which gets installed after the last smoke detector on the circuit. I'll have to check on make/model information for you if you need that.

AFAIK, no one makes a combined smoke/CO (not CO2, by the way) detector. Even if they did, I'd be inclined to use separates. These are two distinct hazards and require different response. Consider what someone might do if a unit went off on a cold winter night and they thought it was detecting smoke. The homeowner might make sure the family is safe (perhaps evacuate) and check the house to see if there's a fire. Finding no fire or smoke, he decides all is well and resets the detector or silences the alarm control panel. Everyone goes back to bed. But the problem isn't smoke. The furnace flue is blocked and the house is filling with carbon monoxide.

You may wish to determine if there's a relay module for your brand of (existing) smoke detectors. If so, connect that to the Caddx panel and you're home free on fire detection. Add a separate zone or zones for CO detection.

In case you're interested, I have a lot of information on CO detectors on my web site. I also have an extensive FAQ on alarms and automation in general, as well as links to numerous other good FAQ sites.