This pollutant is produced by the incomplete burning of fuels (or the incomplete combustion of natural gas, coal, wood, etc.).  Common sources of carbon monoxide are unvented gas space heaters, gas stoves, fireplaces, generators, gasoline-powered equipment, including automobiles.  In particular, dangerous sources can be old or poorly functioning combustion devices.  In certain quantities, this pollutant can pose immediate threats to human health.

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