PRODUCT DESCRIPTION This handy 2-pack of FIRST ALERT CO400 Carbon Monoxide Alarms utilizes electrochemical carbon monoxide sensors to monitor your space for carbon monoxide threats. The battery-powered design doesn't require an electrician; simply insert the included 9-volt battery into each alarm, and the carbon monoxide detectors are ready to go. The advanced electrochemical CO sensors detect carbon monoxide leaks from multiple sources, such as faulty fuel-burning appliances, blocked chimneys, and generators running inside or too close to homes. When CO levels become elevated, a loud 85-decibel alarm alerts you to the threat. Because CO evenly distributes itself, it's important to have a CO detector on every level and in every bedroom of your home. Designed to be simple to use, each CO detector has just one button that silences or tests the unit, as well as an end-of-life timer that lets you know when it's time to replace the device. Carbon monoxide (CO) is the leading cause of accidental poisoning deaths in America, 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 CO400-3 carbon monoxide alarm uses an electrochemical carbon monoxide sensor, the most accurate technology available. The permanent sensor lasts up to five years. It is powered by 1-9V replaceable battery per alarm giving you peace of mind even during power outages. The test/silence button both silences the alarm and allows you to test its functionality. The unit monitors and re-alarms if carbon monoxide levels persist, sounding a loud 85-decibel horn. No installation is required and the attractive design allows the unit to be placed anywhere you need it. It includes an optional wall mount with no outlet required. An audible and visual low battery signal alerts you to replace the battery. Pull down action chart has convenient guide on what to do if an alarm sounds. For use in all 50 states; compliant with current CO Laws in California, Wisconsin, and Oregon. 5 year limited warranty. UL listed. FROM THE MANUFACTURER Carbon monoxide (CO) is the leading cause of accidental poisoning deaths in America, yet many people don't know they are suffering from CO poisoning until its 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 CO400CN2 2-Pack carbon monoxide alarm uses an electrochemical carbon monoxide sensor-the most accurate technology available. The permanent sensor lasts up to five-Years. Battery access in back of unit, 9 Volt battery included. The test/silence button both silences the alarm and allows you to test its functionality. The unit monitors and re-alarms if carbon monoxide levels persist sounding a loud 85-Decibel horn. No installation is required and the attractive design allows the unit to be placed anywhere you need it. It includes an optional wall mount with no outlet required. An audible and visual low battery signal alerts you to replace the battery. Pull down action chart has convenient guide on what to do if an alarm sounds. 5-Year limited warranty. UL listed.