Carbon monoxide, or CO, is a poisonous gas. You cannot see it or smell it. If too much CO leaks into your home, you can become very sick or even die from it. Carbon monoxide is produced when equipment and appliances that burn fuels are operating. Electric appliances do not produce CO. If your home has fuel-burning appliances or an attached garage, you should have at least one carbon monoxide alarm installed. Put them near the places where people sleep.