The Alecto COA-29/17 is a carbon monoxide detector. Carbon monoxide is a gas that we do not smell, taste and see. That is why it is important to have a carbon monoxide detector at home. The Alecto COA-29/7 contains batteries with a lifetime of 7 years. The detector gives a warning when the batteries are almost empty. With a carbon monoxide detection, an audible signal sounds 85 dB. Then it is up to you to immediately open all windows and doors and leave your home.