Less than half the diameter and offering the same protection, the First Alert® SM210M 10-Year Sealed-Battery Micro Smoke Alarm meets the latest industry standards using First Alert's Precision Detection advanced sensing technology. It reduces cooking nuisance alarms and provides early warning in the event of a home fire emergency. The small but mighty smoke detector is easy to install and doesn't require battery replacements. Instead, its end-of-life warning lets you know when it’s time to replace the alarm. No more low-battery chirps and multiple battery replacements!