Volatile organic compound

A volatile organic compound (VOC) is a carbon-containing chemical that readily enters the air as a gas under ordinary conditions. VOCs occur in natural emissions and human-made products, and some affect health or air quality.

Vapor pressure: The pressure exerted by a substance’s vapor when it is in equilibrium with its liquid or solid phase. Higher vapor pressure generally makes a chemical more likely to evaporate into indoor or outdoor air.
Gas chromatography–mass spectrometry: An analytical technique that separates compounds by gas chromatography and identifies them by mass spectrometry. It can identify and quantify individual VOCs in air samples.
Organic compound: A chemical compound built around carbon, usually bonded to hydrogen or other elements. VOC classifications apply to organic compounds, with some definitions excluding particular carbon-containing substances.
Formaldehyde: A reactive, volatile organic compound used in resins and produced by combustion and other chemical processes. It is a common indoor VOC associated with irritation and cancer risk.
Henry's law: A relationship describing how a dilute substance partitions between a gas and a liquid at equilibrium. It helps predict whether VOCs escape water into air or remain dissolved.
Photoionization detector: A detector that uses ultraviolet light to ionize gases and measure their combined response. Portable instruments use it for rapid screening of many airborne VOCs.
Volatility: The tendency of a substance to vaporize under given conditions. A compound’s volatility is the property that lets it enter air readily.
Benzene: A volatile aromatic hydrocarbon found in fuels and combustion emissions that causes cancer in humans. It illustrates how a VOC can pose serious long-term risks even at relatively low exposure.
Photochemical smog: Air pollution formed when sunlight drives reactions among nitrogen oxides and reactive organic compounds. Many VOCs supply the organic reactants that help produce ground-level ozone and smog.
Indoor air quality: The condition of air inside buildings as it relates to occupants’ health and comfort. VOC emissions from materials and activities are one part of indoor air quality.

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