"Volatile organic compounds" (VOCs) are the collective term for organic, i.e. carbon-containing substances which evaporate easily (are volatile) or are already present as a gas at low temperatures (e.g. room temperature). In the abbreviation NMVOCs (non methane volatile organic compounds), which is also used very frequently, the gas methane, CH4, is excluded from the group of VOCs.
The word volatile implies that the substances belonging to the VOC group evaporate rapidly (evaporate) due to their high vapour pressure or low boiling point. Volatile organic compounds are classified according to the WHO according to their boiling point or the resulting volatility:
Classification of VOC boiling range
1. very volatile organic compound (VVOC) < 0 to 50...100 °C
2. volatile organic compound (VOC) 50...100 to 240...260 °C
3. semi volatile organic compound (SVOC) 240...260 to 380...400 °C
4. organic compound associated with particulate matter or particulate organic matter (POM) 380 °C
However, there is no uniform definition of what a VOC actually is. Some definitions actually contain data on vapour pressure, others, usually more recent definitions, define VOCs via their photochemical reactivity as precursors for the formation of ground-level ozone. In addition, some definitions explicitly exclude certain organic substances from the VOC definition. For the assessment of indoor air, another definition is common. This also applies to the emission of VOCs from products into indoor air.
VOCs are emitted into the environment by a variety of anthropogenic and biogenic processes. Plants, animals, soils and oceans are natural sources; industrial solvent use and transport are among the most important anthropogenic sources.
All living beings (humans, animals, plants, microorganisms) emit organic compounds into the environment. For example, swamps are huge sources of methane. Many plants emit terpenes and other organic substances.
The human release of volatile organic compounds is dominated by the use of solvents and road traffic. If methane emissions from rice cultivation are regarded as an anthropogenic source of VOCs, this is also a significant source. In addition to VOCs in the atmosphere, volatile organic compounds are also found in indoor air.
Sources of these VOCs include plastics, building materials, furniture and carpets, cleaning agents and the consumption of tobacco products.
Effects on health
People can become permanently ill as a result of exposure to volatile organic compounds in indoor air. Children, the elderly and sensitive people are most frequently affected. Symptoms such as headaches, allergies, fatigue, reduced performance, sleep disorders and irritation of the respiratory tract are summarised under the term "Sick Building Syndrome". The clinical picture is defined internationally by the WHO.
Emissions in the automotive industry
The automotive industry also has limit values for hydrocarbon emissions, which are generally referred to as HC emissions.