A video on the Kidde Smoke and Carbon Monoxide Detector (Alarm).
This system uses 3 AA batteries prefer alkaline types.
This system talks when there are fire or carbon monoxide gas in the house. I had a few of these unit before and they only last about 7 years however it's a good piece of mind to have at least one. This is since the radioactive particle for finding smoke disappears.
Some cities and states requires each home to have among these units nowadays.
Keep in mind to change the batteries every 6 months or a year.
The paperwork on these units can be found at: