Smoke alarms have saved thousands of lives in the United States since their introduction and widespread use during the past 2 decades. The good news is that more than 90% of homes in the United States now have at least 1 smoke alarm.1 The bad news is that a substantial proportion of those smoke alarms do not work. In on-sitesurveys of homes with smoke alarms, about 25% to 30% of the alarms did not function when tested.2 Some failures are due to malfunction of the alarm itself, some are due to a dead battery, and some do not function because the battery has been removed.

— Smoke alarms and prevention of house-fire—related deaths and injuries

If dead batteries are a problem, we could power them using solar panels and ambient light. The current panels probably aren’t efficient enough yet, but that’s improving.