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
ECONOMIZER: any mechanical device that adjusts
to variable conditions to maximize energy efficiency;
a control option in ventilation systems that makes
optimum use of outside supply air, providing free
cooling. During the economizer cycle, the
system adjusts dampers according to the comparison
between return air and outside air temperatures
to meet the required air temperature.
ECZEMA: an acute or chronic non-contagious inflammatory
condition of the skin that is characterized by
redness, itching, and oozing vesicular lesions
often caused by exposure to an irritant or chemical.
EFFECTIVE AREA: The calculated area of an outlet
based on the averaged measured velocity between
EFFECTIVE TEMPERATURE: The uniform temperature
of a radiantly black enclosure at 50% relative
humidity, in which an occupant would experience
the same comfort, physiological strain and heat
exchange as in the actual environment with the
same air motion.
ELECTRONIC PRECIPITATOR: Also called Electronic
Air Cleaner (EAC); uses a high voltage between
two conductors to remove particles (dust, etc.)
from the air flowing through it.
EMISSION: the release of airborne contaminants
from a source.
EMISSION RATE: a measure of the amount of a contaminant
released from a source surface per unit time,
expressed in units such as mg/m2-hr; or the concentration
of a contaminant from a source that is present
in the air space surrounding the source, expressed
in units such as parts per million or m g/m3
EMISSION STANDARD: a voluntary guideline or government
regulation that specifies the maximum rate at
which a contaminant can be released from a source.
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EMPHYSEMA: A respiratory in human beings characterized
by a loss of elasticity in the alveoli or lung
ENCAPSULATION: a mitigation technique that reduced
or eliminates emissions from a source by sealing
with an impenetrable barrier.
ENDOTOXINS: Harmful substances that are contained
within the cells that produce them, or are integral
constituents of cellular structure and are not
released until the cell disintegrates.
ENERGY: Expressed in kilowatt-hours (kWh) or
watt-hours (Wh), and is equal to the product of
power and time.
energy = power X time
kilowatt-hours = kilowatts X hours
watt-hours = watts X hours
ENTHALPY: The total quantity of heat energy contained
in a substance, also called total heat; the thermodynamic
property of a substance defined as the sum of
its internal energy plus the quantity Pv/J, where
P = pressure of the substance, v = its volume,
and J = the mechanical equivalent of heat.
ENTRAINMENT: The capture of part of the surrounding
air by the air stream discharged from an outlet
(sometimes called secondary air motion).
ENTRAINMEMT VELOCITY: The gas flow velocity,
which tends to keep particles suspended and cause
deposited particles to become airborne.
ENTROPHY: The ratio of the heat added to a substance
to the absolute temperature at which it is added.
ENVIRONMENTAL TOBACCO SMOKE (ETS): the combination
of side-stream and mainstream smoke that is emitted
from a burning cigarette; also called second hand
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EPIDEMIC: A sudden increase in frequency of a
disease, above the normal expectancy, in a population
of human beings.
EPIDEMIOLOGY: The field of science that concerns
itself with the determinants of disease and with
the factors that influence its distribution.
EPIDERMIS: The outer layer of human skin, composed
of a thin layer of epithelial cells.
EQUAL FRICTION METHOD: A method of duct sizing
wherein the selected duct friction loss value
is used constantly throughout the design of a
low-pressure duct system.
EQUILIBRIUM: the point at which the entry or
creation rate of a contaminant equals the removal
ERYTHEMA: an abnormal redness of the skin due
to capillary congestion.
ETIOLOGICAL: Pertaining to the cause of a disease
or abnormal condition.
EVAPORATION: Change of state from liquid to vapor.
EVAPORATION RATE: The ratio of the time required
to evaporate a measured volume of a liquid to
the time required to evaporate the same volume
of a reference liquid (ethyl ether) under ideal
test conditions. The higher the ratio, the slower
the evaporation rate.
EVAPORATIVE COOLING: The adiabatic exchange of
heat between air and a water spray or wetted surface.
The water approaches the wet-bulb temperature
of the air, which remains constant during its
traverse of the exchanger.
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EVAPORATOR: The heat exchanger in which the medium
being cooled, usually air or water, gives up heat
to the refrigerant through the exchanger transfer
surface. The liquid refrigerant boils into a gas
in the process of the heat absorption.
EXFILTRATION: The movement of air out of a building,
through cracks and other openings, such as around
windows and doors.
EXHAUST: the indoor air that is removed from
EXOTHERMIC: A reaction in which heat is given
off as in a fire, or in the combination of water
and lithium bromide.
EXOTOXIN: Harmful substance produced within cells,
but excreted from intact cells into the surrounding
EXTRINSIC ALLERGIC ALVEOLITIS: A swelling from
of pneumonia that is caused by an immune reaction
in an allergic patient. The reaction may be brought
about by a variety of inhaled organic dusts, often
those containing fungal spores. A wide variety
of symptoms may occur, including difficulty breathing,
fever, chills, malaise, and muscle aches. The
symptoms usually develop 4 to 6 hours after exposure.
Kinds of extrinsic allergic alveolitis include
bagassosis, farmer's lung, humidifier or air conditioner
lung, mushroom worker's lung, suberosis. Also
called hypersensitivity pneumonitis.
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