The Kidde Lifesaver 5CO features two LED lights: a red LED that illuminates when the alarm detects CO in the atmosphere and a green LED that confirms DC power is present and the alarm is operational. This alarm can be installed on a wall or placed on a table top or shelf for added convenience. It's ideal for use when on holiday or in rented accommodation. The Lifesaver 5CO features a seven year sensor life with an end of life warning to replace the unit after seven years of protection.