VOCs: Volatile Organic Compounds
In general, volatile organic compounds (VOCs, also known as volatile organic chemicals or volatile organic constituents) are carbon-containing chemicals that tend to evaporate readily, but there is no universally-accepted technical definition. Some sources define VOCs as organic chemicals that boil at less than 200 degrees Fahrenheit; other definitions reference a vapor pressure of greater than 0.1 millimeters of mercury under standard conditions. The likely reason for the lack of a standard definition is that volatility is a continuous variable, like temperature, and not a binary one.
The US EPA's Terms of Environment (now archived) defines a VOC as "Any organic compound that participates in atmospheric photochemical reactions except those designated by EPA as having negligible photochemical reactivity." If that's not confusing enough check out the defintion in the U.S. Code of Federal Regulations at 40 CFR Part 51.100(s) (Link is via the Iowa Department of Natural Resources). Wikipedia adds to the fun by throwing in some international definitions.
However defined, there are many different VOCs. Environmental regulations focus on a relatively small fraction of those, generally VOCs that see wide industrial use, are breakdown products of industrial chemicals, and/or are compounds known to be particularly toxic.
There are many laboratory methods for analyzing VOCs. One of the most widespread is EPA's SW-846 Method 8260. However, there are several variants of this method, each of which lists a somewhat different set of chemicals, but all of the variants include most of the volatile organic chemicals that attract the lion's share of interest at hazardous waste sites. Here is a list of the chemicals included in Method 8260B:
Acetone
Acetonitrile
Acrolein
Acrylonitrile
Allyl alcohol
Allyl chloride
Benzyl chloride
Bis(2-chloroethyl)sulfide
Bromoacetone
Bromochloromethane
Bromodichloromethane
Bromoform
Bromomethane
n-Butanol
2-Butanone
tert-Butyl alcohol
Carbon disulfide
Carbon tetrachloride
Chloral hydrate
Chlorobenzene
Chlorodibromomethane
Chloroethane
2-Chloroethanol
2-Chloroethyl vinyl ether
Chloroform
Chloromethane
Chloroprene
3-Chloropropionitrile
Crotonaldehyde
1,2-Dibromo-3-chloropropane
1,2-Dibromoethane
Dibromomethane
1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
cis-1,4-Dichloro-2-butene
trans-1,4-Dichloro-2-butene
Dichlorodifluoromethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethene
cis-1,2-Dichloroethene
trans-1,2-Dichloroethene
1,2-Dichloropropane
1,3-Dichloro-2-propanol
cis-1,3-Dichloropropene
trans-1,3-Dichloropropene
1,2,3,4-Diepoxybutane
Diethyl ether
1,4-Dioxane
Epichlorohydrin
Ethanol
Ethyl acetate
Ethylbenzene
Ethylene oxide
Ethyl methacrylate
Hexachlorobutadiene
Hexachloroethane
2-Hexanone
2-Hydroxypropionitrile
Iodomethane
Isobutyl alcohol
Isopropylbenzene
Malononitrile
Methacrylonitrile
Methanol
Methylene chloride
Methyl methacrylate
4-Methyl-2-pentanone
Naphthalene
Nitrobenzene
2-Nitropropane
n-Nitroso-di-n-butylamine
Paraldehyde
Pentachloroethane
2-Pentanone
2-Picoline
1-Propanol
2-Propanol
Propargyl alcohol
B-Propiolactone
Propionitrile
n-Propylamine
Pyridine
Styrene
1,1,1,2-Tetrachloroethane
1,1,2,2-Tetrachloroethane
Toluene
o-Toluidine
1,2,4-Trichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichlorofluoromethane
1,2,3-Trichloropropane
Vinyl acetate
Vinyl chloride
Xylene
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