environmental consultants environmental consulting

Environmental Consultants

Phone: (800) 464-5285

IAQ Glossary V


A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z

VANEAXIAL: A type of fan completely contained in a section of round duct.

VAPOR: A substance in gas form, particularly one near equilibrium with its condensed phase and which does not follow the ideal gas laws; in general, any gas below its critical temperature.

VAPOR BARRIER: A moisture-impervious layer applied to the surfaces enclosing a humid space to prevent moisture travel to a point where it may condense due to lower temperature.

VAPOR PRESSURE: Vapor pressure denotes the lowest absolute pressure that a given liquid at a given temperature will remain liquid before evaporating into its gaseous form or state.

VARIABLE AIR VOLUME (VAV): A supply air system that holds the supply air temperature constant but varies supply air flow to compensate for the thermal loads in the space.

VARIABLE AIR VOLUME BOX: the terminal device of a VAV system that controls the volume of conditioned air admitted from the air supply.

VARIABLE VOLUME VARIABLE TEMPERATURE: an HVAC system that combines variable air volume with variable temperature to provide greater low-load airflow to the conditioned space than that provided by standard VAV systems.

VEHICLE: Any contaminated inanimate material, such as water or food, through which microorganisms can be transported or dispersed to a susceptible host.

return to top

VELOCITY: A vector quantity which denotes, at once, the time rate and the direction of a linear motion.

VELOCITY, OUTLET: The average discharge velocity of primary air being discharged from the outlet, normally measured in the plane of the opening.

VELOCITY PRESSURE: The pressure produced by the movement of air, such as the wind, or the air coming from a fan.

VELOCITY, TERMINAL: The highest sustained air stream velocity existing in the mixed air path at the end of the throw.

VENTILATION: The process of supplying and removing air by natural or mechanical means to and from any space. Such air may or may not be conditioned.

VENITLATION CONTROL: an air pollutant strategy that uses ventilation to remove and/or dilute pollutants to levels at which they do not present a threat to health and comfort.

VENTILATION EFFECTIVENESS: a measure of the fraction or percentage of outdoor air that reaches the occupied zone of a specified area; an evaluation of air delivery to occupants, regardless of the effectiveness of contaminant removal.

VENTILATION EFFICIENCY: an evaluation of the pollutant removal capacity of a ventilation system, as defined by the local mean age of air in the exhaust divided by the mean age of air in the room.

return to top

VENTILATION RATE: the rate of intake of outdoor air into indoor spaces.

VENILATION STANDARD: a specification for the minimum rate of input of outdoor air into indoor spaces.

VIRUS: An infectious agent that contains either RNA or DNA in its core surrounded by a protein shell, is able to alternate between intracellular and extracellular states, and replicates only when present in living cells.

VOC: “Volatile Organic Compound” Any organic chemical reacting with atmospheric ozone. This designation is not a reflection or indication of human health effects.

VOLATILE FUMES: The fumes from substances such as gasoline or alcohol; usually very flammable.

VOLATILITY: the tendency of a molecule to exist in a gaseous state.

VOLUME: Cubic feet per pound of dry air in the air-water vapor mixture as used in pschrometrics.

VOLUME, SPECIFIC: The volume of a substance per unit mass; the reciprocal of density.

return to top

Home | Residential | Commercial | Forensics | Well Building | Newsletter | Information Request | Glossary | Links | Contact Us
Copyright © 2011 Indoor Air Diagnostics. All rights reserved.