The Kidde Lifesaver 5CO features two LED lights; the red LED illuminates when the alarm has detected CO in the atmosphere and the green LED confirms that DC power is present and the alarm is operational. The alarm can either be installed on a wall or just placed on a table top or shelf for added convenience. It is also ideal for use when on holiday and 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.7 year sensor life2 LED indicator lightsContinuous protection against CO2End of life warning