Product Description The First Alert CO400 carbon monoxide alarm uses an electrochemical sensor the most accurate technology available. The permanent sensor lasts up to 5 years. It is powered by a 9V replaceable battery giving you peace of mind even during power outages. The test/silence button silences the alarm and allows you to test its functionality. The unit monitors and re alarms if carbon monoxide level 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 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. Amazon.com 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 CO400 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 on 9V replaceable battery 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. 5 year limited warranty. UL listed. --Bree Norlander P.when('A').execute(function(A) { A.on('a:expander:toggle_description:toggle:collapse', function(data) { window.scroll(0, data.expander.$expander[0].offsetTop-100); }); }); Manufacturer Contact Information 1 (800) 323-9005. See more Keep your family safe with this easy to use, battery operated carbon monoxide alarm; Battery powered alarms provide continuous monitoring of CO levels, even if there's a power failure Features an advanced electrochemical carbon monoxide sensor that accurately detects carbon monoxide levels, no matter where the detector is placed in the room.The alarm sequence should last 5-6 seconds. If it does not alarm, make sure fresh batteries are correctly installed, and test it again. If the unit still does not alarm, replace it immediately A loud 85 decibel alarm sounds when CO levels reach dangerous , Battery Replaceable - Yes To ensure complete protection make sure to place one on each level of your home and in each bedroom 5-year limited warranty; Equipped with end of life signal chirp, so you know when its time to replace the unit for safety All first alert CO alarms are rigorously tested to meet UL standards First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert Brand Trust Survey in February 2018)