Carbon monoxide (CO) is one of the leading causes of accidental poisoning deaths, yet many people don't know they are suffering from CO poisoning until it’s too late. Since symptoms of CO poisoning are like the flu, you might not even know you're in danger at first. That's why a carbon monoxide alarm is an excellent way to protect your family. It can detect the CO you can't see, smell or taste in the air. The First Alert SCO5RVA carbon monoxide and smoke alarm uses an electrochemical carbon monoxide sensor-the most accurate technology available. The alarm uses photoelectric smoke sensing technology which is environmentally friendlier and which reduces nuisance alarms, making it ideal for cooking areas. It is also great for sensing slow smoldering fires quickly. The permanent sensors last the lifetime of the alarm. The test/silence button both silences a non-threatening alarm or low battery warning and allows you to test the unit's functionality. The alarm uses different 85-decibel horns and lights depending on whether it's alerting you to smoke or carbon monoxide. The end-of-life alarm provides three chirps that alerts you to replace the unit. 2 AA batteries are included. UL listed. The First Alert SCO5RVA Battery Operated Combination Carbon Monoxide/Smoke Alarm comes with a 5-year limited warranty. First Alert is the most trusted brands in home safety. Our mission is helping protect the lives, well being and the valuables of our customers.