Electronic Alarms and Home Security Devices - Installing Hard-Wire CO Detector

My house is two years old and has hard-wired interconnected smoke detectors (Firex FADC #5000). I want to add a CO detector in the hallway outside the bedrooms. I read that CO detectors should be at least 5 feet off the floor. Rather than have a cord going up the wall from an outlet, my thought is to replace the smoke detector on the ceiling with a combination smoke/CO detector like Kidde 900-0114 KN-COSM-IB. Does this make sense? I've replaced electrical fixtures in the past, so I think I could do this myself. But I am wondering if there is anything I need to consider before undertaking this.

Are the smoke detectors wired into an alarm system? Do the all sound if one sounds? Then I wouldn't change it unless I got one that works with the others.

If it just runs on AC then you can swap it out. OR just mount a CO detector beside the smoke alarm, they normally work on their own power (battery) anyway.

Thanks for your message! These smoke alarms ARE interconnected (when one goes off, they all do), but they are not connected to a security system. I did some checking on the FIREX web site, and I see that they do have a smoke/CO combo detector that will work with our currect smoke detectors and will allow me to replace the smoke unit in the hallway with the combo unit: FIREX 7000. Thanks for the help.