CO sensor end-of-life timer feature: When the CO sensor has passed end-of-life, a trouble signal will be sent to the module then to the FACP. This indicates that the CO sensor inside the detector must be replaced. If unresolved for 30 days, the detector will chirp intermittently. The typical life of the CO sensor is ten years from the date of manufacture; it is recommended to periodically
check the “Replace by” sticker located on the replaceable CO cell.