How to Prepare for an Emergency
Install many. Mount one on every level of the house and outside all sleep areas.
Check the batteries regularly. Test them once a month and replace them at least once a year, unless you have units powered by 10-year lithium batteries (these still require monthly checking). Some smoke alarms are connected to the household electrical system and may or may not have a battery backup. It’s important to test these monthly, too. Regardless of the power source, buy new smoke alarms every 10 years.
Keep alarms clean. Dust and debris can cause malfunctions, so vacuum or dust alarms regularly.
Never disable an alarm. Newer detectors have hush buttons, so you won’t have to compromise the alarm’s power source just because you charred your toast.