Total hydrocarbons (THC, CH4 and NMHC)

The term "total hydrocarbons" (THC) refers to a broad family of chemicals that contain carbon and hydrogen atoms. Methane (CH4), a non-reactive hydrocarbon, is the most common hydrocarbon in the earth's atmosphere. Specific reactive hydrocarbons or non-methane hydrocarbons (NMHC) can react with oxides of nitrogen in the presence of sunlight to form ozone. Health effects may result at varying concentrations depending on the hydrocarbon. Alberta has ambient air quality objectives for specific hydrocarbons. For more information on Alberta’s Ambient Air Quality Objectives please go to

Sources of hydrocarbons include vegetation, vehicle emissions, gasoline marketing and storage tanks, petroleum and chemical industries, dry cleaning, fireplaces, natural gas combustion and aircraft traffic. Hydrocarbons are also emitted by fugitive sources such as evaporation of solvents, or leaking valves, flanges, pumps and compressors at industrial facilities. Incinerator and flare stacks can also be sources of hydrocarbons.

Hydrocarbon concentrations are highest in the winter at monitoring stations located close to major traffic arteries. In downtown Edmonton and Calgary, maximum hydrocarbon values are observed during the morning and afternoon rush hours. Vehicles are the major source of hydrocarbons at urban locations.

Monitoring Method

Hydrocarbons are monitored continuously by a hydrogen flame ionization detector. When burned, carbon hydrogen bonds break creating ions that conduct an electric current. This current is then measured by an electrometer to give a signal proportional to the number of ions.


Alberta does not have ambient air quality Objectives for hydrocarbons. Many hydrocarbons, such as CH4, are emitted by natural sources. Normal background THC concentrations recorded in rural Alberta range from 1.5 to 2 ppm. Background hydrocarbons are primarily composed of CH4 with a small contribution from NMHC (about 0.2 ppm).

Get Involved

As an airshed, educating about air quality is an essential part of what we do. It is important to us as an organization to inform through not only sharing air quality data but also providing tips on how we can all do our part to reduce air pollution and serve as environmental stewards at an individual level.

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