I bought only one combo ionic and Carbon Monoxide alarm to replace a ionic alarm in the living room. No problems, no false alarms. Easy to install, as I just switched it out with existing ionic alarm with the combo. I sell homes on the Central Coast of California and the new CA state law requires each home to have one working carbon monoxide alarm on each floor. You may as well have a combo smoke a carbon monoxide alarm as the price for the Kidde is about the same or even cheaper.I would recommend buying carbon monoxide alarms before you put your home on the market, because you have to buy them anyway before you sell your home. For more information or Homes on the Central Coast of California go to my web site at [...]