KiddeSmoke & Carbon Monoxide Detector, Combination Smoke & CO Alarm with Lithium Battery, Replacement Alert, White, P3010k-CO, SmartHush

Works for about 10 years. Will chirp when it is ready for replacement. Big box store (HD) sells this in plastic retail packaging for 50% more. If you order this from Amazon (I ordered the double pack) it arrives in labeled cardboard packaging. It comes with instructions and mounting screws. I also includes the mounting plate. You screw it into your ceiling and once the plate is secure, it is a quarter turn clockwise to lock it in place and to activate. In 10+ years it will chirp and you reverse the process and buy a new one. Don't be fooled into thinking that the ones that take 9v or AA batteries will last indefinitely with battery changes... they still wear out and will chirp when they need replacement. These are effective and save you the hassle of frequent battery changes.

Easy to use just turn it on the supplied mounting bracket and it activated

Had to replace the unit in my kitchen as the battery finally started chirping. Old unit only lasted eight years not ten but still it is worth the peace of mind. Easy to replace and just unscrewed old Kidde and screwed on new one. Works perfectly thank you.

Simply install the back plate on a wall (high enough) or the ceiling with the supplied screws.Remove the plastic cover from the detector; it will beep once, loudly. Watch your ears.There is nothing else you need to do for the next 10 years!

The make is always high quality, and I like that the battery lasts many years. I forget when I bought it before, but I don't want to change the battery every year. It is not safe to do that unless you have a supply of batteries at home all the time.