One of the most common terms used in the solvents industry is “VOC” — as in “reduced-VOC,” “non-VOC,” and “VOC content.” Most people in the industry know that “VOC”stands for “volatile organic compound,” but many do not fully understand what VOCs are and why they receive so much attention. This bulletin briefly outlines some of the basic concepts associated with VOCs.

VOCs and Ozone Formation

With certain important exceptions discussed below, the solvents used in products such as coatings, inks, adhesives, and consumer products, are generally classified as VOCs. Unless they are controlled (by an incinerator on a painting operation, for example), these solvents are emitted into the air after they perform their function. Thus,solvent emissions from products and industrial operations are one of several significant sources of VOC emissions.

The accompanying pie chart,which is based on data from the U.S. Environmental Protection Agency (EPA), shows the relative contribution of all man-made sources of VOC emissions. Vehicles are the largest source of VOC emissions nationwide, and other significant sources include petroleum production and distribution and industrial combustion. There are also significant VOC emissions from natural or “biogenic” sources such as trees and other vegetation.

Emissions of VOCs, in and of themselves, do not necessarily give rise to health or environmental concerns. In many areas,however, they react with oxides of nitrogen (NOx) in the presence of heat and sunlight to form ground-level ozone — the primary component of “smog.”For that reason, they are regulated as “ozone precursors” under the federal Clean Air Act and similar state laws.

In order to reduce ozone levels, federal and state agencies have developed regulations to reduce VOC emissions from a variety of sources, including products that contain solvents. In some cases (for major coating operations, for example), these regulations require the installation of a control device such as an incinerator or a solvent recovery system. In other cases, they limit the amount of solvent that can be used in products. They do not prohibit the use of solvents, due to the essential role solvents play in a variety of products and processes.

Definition of a VOC

Because VOCs are subject to regulation, the question “What is a VOC?” is a crucial one. The EPA has established a general definition of a VOC that is very broad. In effect, it states that “any volatile compound of carbon” is classified as a VOC for regulatory purposes, unless it appears on a list of compounds that have been specifically exempted. See 40 CFR 51.100 (s).This list of VOC-exempt compounds is discussed below.

EPA’s VOC regulations, however, do not always apply to all compounds that meet the very broad definition found at 40 CFR51.100(s). For example, for regulations involving paints and coatings, there is a specific test method, known as Test Method 24, that generally determines what is to be treated as a VOC. See 40 CFR part60, Appendix A. Test method 24 is a collection of ASTM test methods that collectively defines the VOC content of a coating formulation. Generally any non-exempt compound (discussed further below) that is “picked up” by these test methods is considered a VOC for purposes of regulating coating formulations.

Individual states have their own VOC definitions, including their own list of exemptions. Although state definitions (including exemptions) are generally the same as the EPA definition, a solvent user should be aware of the precise definition that applies in his or her state.

source: american solvents council