Did you know fuel-burning appliances, blocked chimneys, and running cars are all carbon monoxide threats? Secure your home or business against them with the First Alert Digital Carbon Monoxide Detector 3-Pack (CO410). Using an electrochemical carbon monoxide sensor that can sense gas even when it cant be seen, smelled, or tasted, its easy-to-read digital display provides a quick view of current, peak, and dangerous CO levels, and illuminates when the button is pressed or an alarm is triggered. Once a threat is detected, the 85-decibel siren sounds, even in the event of an electricity failure or power outage. The low-battery indicator alerts you when it needs to be replaced, while the end-of-life signal notifies you when the detector is nearing expiration. Ensure its functioning properly with the test button that doubles as an alarm silencer. Its easy-to-use design doesn't require an electrician: Simply open the EZ access door, insert the included AA batteries, and the carbon monoxide detector is ready to go.