Carbon monoxide (CO) is a colorless, odorless and tasteless gas. It’s made by partial fuel combustion usually caused by not enough oxygen. In your residence, appliances that need natural gas, charcoal, wood or kerosene are at risk. Especially if they are not working properly or have been installed wrong.
Vehicle exhaust fumes from neighboring garages, as well as malfunctioning fireplaces could also be a carbon monoxide source. CO is toxic to the body and is fatal at increased levels or with prolonged exposure.