The First Alert SMI100 Battery-Operated Smoke Alarm is easy to install and features First Alert's Precision Detection advance sensing technology. The front access battery compartment makes for quick battery replacements and a low battery warning will advise when it's time to replace. Discourage unwanted removal of the battery or smoke alarm using the optional locking features. Use the convenient test/silence button on the front of the smoke alarm to check that it is operating properly and silence false alarms. An end-of-life warning will advise you when it’s time to replace because alarms don't last forever. Effortlessly install the CO400 Battery-Operated Carbon Monoxide Alarm throughout your home for reliable CO protection in minutes. Operation is simple. Test the CO alarm using the single test/silence button. The low battery warning will notify you when it's time to replace the alarm's battery, which is quick process due to the front access battery door, and an end-of-life warning will alert you when it's time to replace the alarm all together.