Smoke alarms are an important part of every household. They can alert you to a fire, even when you're not at home, and can potentially save your life. The First Alert 9120B Smoke Detector is a reliable and affordable option for any home. The First Alert 9120B is a hardwired smoke alarm with a battery backup. This means that even if there's a power outage, the alarm will still work. The ionization sensor is able to detect smoke from fast flaming fires, and the 85 decibel alarm will alert you to the danger. This smoke alarm is easy to install, and it's a great option for any home. Whether you're looking for a primary smoke alarm or a backup, the First Alert 9120B is a great choice.