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 use natural gas, charcoal, wood or kerosene are at risk. Especially if they are not operating properly or have been installed wrong.
Vehicle exhaust fumes from nearby garages, as well as fireplaces that aren’t working right can also be a carbon monoxide source. CO is toxic to the body and is fatal at heightened levels or with prolonged exposure.