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) are important because: (1) they can react with oxides of nitrogen in the presence of sunlight to form ozone; and (2) they can be toxic (at high concentrations) to humans, animals or vegetation.

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.

Objectives
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).

	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) are important because: (1) they can react with oxides of nitrogen in the presence of sunlight to form ozone; and (2) they can be toxic (at high concentrations) to humans, animals or vegetation. 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. Objectives 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).

Hydrocarbons (THC, CH4 and NMHC)

Hydrocarbons (THC, CH₄ and NMHC)