Carbon monoxide has no color, taste or odor. It comes from the incomplete combustion of fuels with carbon, such as oil, coal, wood, gasoline and natural gas. Vehicle emissions account for the largest source. Breathing air with high concentrations of CO can result in multiple health effects.

Since 1971, EPA has maintained two standards for carbon monoxide. The eight-hour standard stands at nine parts per million, and the one-hour standard stands at 35 parts per million. If design values are at or below the standard, then an area is in compliance. Design values correspond to an annual average of eight-hour concentrations and one-hour concentrations. 

Departmental information about carbon monoxide (CO)

  • 1971 standard and related document