Carbon monoxide (CO) is an invisible, odorless and tasteless gas. It’s produced by insufficient fuel combustion often caused by insufficient oxygen. In your house, appliances that consume natural gas, charcoal, wood or kerosene are susceptible. 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 may also produce carbon monoxide. CO is toxic to the body and is fatal at increased levels or with extended exposure.