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• Semivolatile inorganic compounds (SVICs)
• Particulate Matter (PM)
Such compounds and substances when present in an air emission stream are termed haz-
ardous air pollutants (HAPs) and, as such, are subject to regulatory scrutiny. The proper
classifications of HAPs help in understanding the needs of a given air pollution project.
Solution

A. Organic compounds that have a vapor pressure of greater than 1 mm Hg at 25°C are
defined to be volatile. As such, these compounds constitute the family of “volatile
organic compounds” or VOCs. Commonly encountered VOCs are the following:
1. All monochlorinated solvents and several other chlorinated solvents such as
trichloroethylene, trichloroethane, and tetrachloroethane.
2. The simple aromatic solvents such as benzene, xylene, toluene, ethyl benzene, and
so forth.
3. Most of the alkane solvents up to decane (C ).
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B. Some inorganic compounds also meet the definition of volatility just defined (vapor
pressure greater than 1 mm Hg at 25°C. As such, these are the “volatile inorganic
compounds” or VICs. They include inorganic gases (e.g., hydrogen sulfide, chlorine,
and sulfur dioxide).
C. When an organic compound has a vapor pressure of less than 1 but greater than 10 −7
mm Hg, such a compound is classified as being in the “semivolatile organic com-
pounds,” or SVOCs, family. Such organics commonly encountered are as follows:
1. Most polychlorinated biphenolics, dichlorobenzene, phthalates, nitrogen substituted
aromatics such as nitroaniline, and so forth.
2. Most pesticides (e.g., dieldrin, toxaphene, parathion, etc.)
3. Most complex alkanes (e.g., dodecane, octadecane, etc).
4. Most of the polynuclear aromatics (naphthalene, phenanthrene, benz(a)anthracene,
etc.)
D. Likewise, at the same vapor pressure as given in Part C, inorganic compounds are
defined to be “semivolatile inorganic compounds” or SVICs. Elemental mercury is a
semivolatile inorganic.
E. A compound or other substance is defined as being “nonvolatile” if it has a vapor pres-
sure < 10 −7 mm Hg at 25°C. This is also another way of defining a solid. Therefore,
almost all particulate matter (PM) is nonvolatile. Examples of compounds that are
found in PM, which result in such PM being considered HAP, are as follows:
1. The large polynuclear (also polycyclic) aromatics such as chrysene.
2. Heavy metals (e.g., lead, chromium, etc.).
3. Other inorganics (e.g., asbestos, arsenic, and cyanides).
F. It is now appropriate to classify hazardous, undesirable, or otherwise unwanted air
pollutants:
1. Aromatic hydrocarbons: benzene, toluene, xylenes, ethylbenzene, and so forth.
2. Aliphatic hydrocarbons: hexane, heptane, and so forth.
3. Halogenated hydrocarbons: methylene chloride, chloroform, carbon tetrachloride,
1,1-dichloroethane, trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene,
chlorobenzene, and so forth.
4. Ketones and aldehydes: acetone, formaldehyde, methyl ethyl ketone, and so forth.