Carbon Monoxide (CO)

What is carbon monoxide?

CO is a colourless, odourless and tasteless but poisonous gas produced primarily by incomplete burning of fossil fuels.

What are the sources of CO?

Approximately 87% of the CO emitted in Ontario in 2012 came from the transportation sectors. The remainder came from miscellaneous/residential (7%), other CO industrial sources (3%) and smelters/primary metals (3%).

Ontario Carbon monoxide emissions by sector - 2012 Estimates

Chart: Carbon monoxide emissions by sector - 2012

Ontario Carbon monoxide emissions by sector - 2012.
Category Percent
Other Transportation 45%
Road Vehicles 42%
Miscellaneous/Residential 7%
Other CO Industrial Sources 3%
Smelters/Primary Metals 3%

Note: 2012 is the latest complete inventory. Emissions may be revised with updated source/sector information or emission estimation methodologies as they become available.

What are the effects of CO?

CO enters the blood stream and reduces oxygen delivery to the organs and tissues. People with heart disease are particularly sensitive. Exposure to high levels is linked with impairment of vision, work capacity, learning ability and performance of difficult tasks.

The Ontario Ambient Air Quality Criteria (AAQC) for 1-hour average CO concentrations is 30 parts per million (ppm), which has been incorporated into Ontario’s Air Quality Health Index to better protect Ontarians. For more information on how the Air Quality Health Index has been modified for reporting in Ontario, please visit the Frequently Asked Questions.