What cause your furnace to produce carbon monoxide.

When a gas and oil furnace is not maintained, the flame doesn't burn properly, it can cause carbon monoxide gas to be released. A crack or hole in the heat ex-changer and a leaking or plugged flue pipe can also release the gas. Carbon monoxide is odorless and colorless, so it can be present and you will not know it. The symptoms are only mild, producing headache, nausea, or fatigue, followed by unconsciousness.