Model to Calculate Concentrations on Elevated
VCM— Vinyl Chloride Monomer
VCP— Voluntary Cleanup Program
VE— Visual Emissions
VEO— Visible Emission Observation
VHS— Vertical and Horizontal Spread
VHT— Vehicle-Hours of Travel
VISTTA— Visibility Impairment from
Sulfur Transformation and Transport in the
VKT— Vehicle Kilometers Traveled
VMT— Vehicle Miles Traveled
VOC— Volatile Organic Compounds
VOS— Vehicle Operating Survey
VOST— Volatile Organic Sampling Train
VP— Vapor Pressure
VSD— Virtually Safe Dose
VSI— Visual Site Inspection
VSS— Volatile Suspended Solids
Vadose Zone— The zone
between land surface and the water table
within which the moisture content is less
than saturation (except in the capillary
fringe) and pressure is less than atmospheric.
Soil pore space also typically contains
air or other gases. The capillary fringe
is included in the vadose zone.
Valued Environmental Attributes/Components—
of ecosystems, human health, and environmental
welfare considered to be important and potentially
at risk from human activity or natural hazards.
Similar to the term “valued environmental
components” used in environmental
Vapor Capture System—
Any combination of hoods and ventilation
system that captures or contains organic
vapors so they may be directed to an abatement
or recovery device.
Vapor Dispersion— The
movement of vapor clouds in air due to wind,
thermal action, gravity spreading, and mixing.
Vapor Plumes— Flue
gases visible because they contain water
Vapor Pressure— A measure
of a substance’s propensity to evaporate,
vapor pressure is the force per unit area
exerted by vapor in an equilibrium state
with surroundings at a given pressure. It
increases exponentially with an increase
in temperature. A relative measure of chemical
volatility, vapor pressure is used to calculate
water partition coefficients and volatilization
permission for a delay or exception in the
application of a given law, ordinance, or
Vector— 1. An organism,
often an insect or rodent, that carries
disease. 2. Plasmids, viruses, or bacteria
used to transport genes into a host cell.
A gene is placed in the vector; the vector
then “infects” the bacterium.
Non-point source pollution control practices
that involve vegetative cover to reduce
erosion and minimize loss of pollutants.
Vehicle Miles Travelled (VMT)—
A measure of the extent of motor vehicle
operation; the total number of vehicle miles
travelled within a specific geographic area
over a given period of time.
Ventilation Rate— The
rate at which indoor air enters and leaves
a building. Expressed as the number of changes
of outdoor air per unit of time (air changes
per hour (ACH), or the rate at which a volume
of outdoor air enters in cubic feet per
The act of admitting fresh air into a space
in order to replace stale or contaminated
air; achieved by blowing air into the space.
Similarly, suction represents the admission
of fresh air into an interior space by lowering
the pressure outside of the space, thereby
drawing the contaminated air outward.
Air pollution control devices that use water
to remove particulate matter from emissions.
Vinyl Chloride— A chemical
compound, used in producing some plastics,
that is believed to be oncogenic.
Virgin Materials— Resources
extracted from nature in their raw form,
such as timber or metal ore.
Viscosity— The molecular
friction within a fluid that produces flow
Volatile— Any substance
that evaporates readily.
Volatile Liquids— Liquids
which easily vaporize or evaporate at room
Volatile Organic Compound
(VOC)— Any organic compound that participates
in atmospheric photochemical reactions except
those designated by EPA as having negligible
Volatile Solids— Those
solids in water or other liquids that are
lost on ignition of the dry solids at 550°
Volatile Synthetic Organic
Chemicals— Chemicals that tend to
volatilize or evaporate.
Volume Reduction— Processing
waste materials to decrease the amount of
space they occupy, usually by compacting,
shredding, incineration, or composting.
Volumetric Tank Test—
One of several tests to determine the physical
integrity of a storage tank; the volume
of fluid in the tank is measured directly
or calculated from product-level changes.
A marked drop in volume indicates a leak.
Assessment of elements in the community
that are susceptible to damage if hazardous
materials are released.
Vulnerable Zone— An
area over which the airborne concentration
of a chemical accidentally released could
reach the level of concern.