It's recommended by the U.S. Fire Administration that you test your smoke detector once every month and make a full ...

If you have an area where you want to add one, install a battery-operated unit, which is about $15. To replace your direct-wired smoke detector, first turn off the power at the main panel.

But one facet of the time change that isn't automatic is that smoke and carbon monoxide ... installing and maintaining fire alarms. In addition to changing the battery periodically, they recommend ...