Carbon monoxide (CO) is a clear, odorless and tasteless gas. It’s produced by insufficient fuel combustion usually caused by insufficient oxygen. In your residence, appliances that consume natural gas, charcoal, wood or kerosene are vulnerable. Especially if they are not working accurately or have been installed wrong.
Vehicle exhaust fumes from attached garages, as well as malfunctioning fireplaces can also be a carbon monoxide source. CO is poisonous to the body and is fatal at high levels or with long exposure.