Carbon monoxide (CO) is an invisible, odorless gas, produced when fossil fuels (like oil, gas or coal) burn. Because you can't see, taste or smell it, carbon monoxide can kill you before you know it's there. Exposure to lower levels over time can make you sick. Install a CO alarm outside each sleeping area and on every level of the home, including the basement, as recommended by the National Fire Protection Association. Ensure that the alarms are plugged all the way in the outlet or, if battery operated, have working batteries installed. Watch this First Alert video for more CO safety tips and information.