WCAS/monitoring/THC
Hydrocarbons are divided into two broad categories, "non-reactive" and "reactive" hydrocarbons. The major non-reactive hydrocarbon is the atmosphere is methane, which is a naturally occurring colorless, odourless gas recognized as a major contributor to the greenhouse effect. The reactive hydrocarbons consist of many volatile organic compounds, some of which react with oxides of nitrogen in the atmosphere to form ozone. They generally occur at much lower concentrations than methane. Total hydrocarbons (THC) include both reactive and non-reactive hydrocarbons.
Large amounts of methane are produced naturally through the decay of vegetation but human activity is contributing to a worldwide increase in methane concentrations of about 1% per year. Trees and plants are major natural emitters of reactive hydrocarbons with other significant sources include motor vehicles, petroleum refineries, petrochemical plants, chemical solvents, vegetation decay and combustion from burning coal, gas and wood.
There are currently no guidelines for Total Hydrocarbons.