With the latest sensing technology, a clear loud alarm and BSI Kitemark approvals, the FireAngel FA3313 Carbon Monoxide Alarm offers the highest level of CO detection for you and your family. The electrochemical sensor in the FireAngel FA3313 Carbon Monoxide alarm provides instant alerts to dangerous levels of CO. It's been rigorously tested and approved by BSI Kitemark to ensure the highest level of safety for your home.