This EI Carbon Monoxide alarm has a high performance, proven electrochemical sensor to sense CO presence. The sensor is individually calibrated and tested in Carbon Monoxide (CO) gas to ensure accuracy. The memory feature records the last CO alarm level and can be useful to check if CO has been present while the home owner or tenant was absent from the property. Features an easy to use Test/Hush button which checks all aspects of the alarm (sensor, electronics, battery and sounder) and an “End of Life” indicator which will notify the user when the alarm needs replacing at the end of its operational life. The alarm has a twist on mounting base which has multiple fixing points so it can easily be secured to a ceiling or wall (screws supplied). For your safety, instructions should be read before installing this product. Requires 2x 1. 5V AAA batteries, included. Audible alarm 85dB at 3m. Tested to BS EN 50291 12010/ BS EN 50291 22010. Comes with manufacturers 5 year guarantee. Always read instructions.