Diverse definitions of the term VOC are in use.

The definitions of VOCs used for control of precursors of photochemical smog used by the EPA, and states in the US with independent outdoor air pollution regulations include exemptions for VOCs that are determined to be non-reactive, or of low-reactivity in the smog formation process. EPA formerly defined these compounds as reactive organic gases (ROG) but changed the terminology to VOC.

In the USA, different regulations vary between states - most prominent is the VOC regulation by SCAQMD and by the California Air Resources Board. However, this specific use of the term VOCs can be misleading, especially when applied to indoor air quality because many chemicals that are not regulated as outdoor air pollution can still be important for indoor air pollution.

VOC sensors
Definitions
Methylene chloride
European Union