ASTM E41-92(2003)
(Terminology)Terminology Relating to Conditioning
Terminology Relating to Conditioning
SCOPE
1.1 These definitions pertain to the conditioning of materials for test purposes. Unless otherwise specified, they are intended to apply to all cases where combinations of atmospheric influences are an essential part of the testing of materials.
1.2 It is the intent of this standard to include those conditioning terms in wide use in ASTM for which standard definitions appear desirable.
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Designation: E 41 – 92 (Reapproved 2003)
Standard Terminology Relating To
Conditioning
This standard is issued under the fixed designation E 41; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope condition, standard—the condition reached by a specimen
when it is in temperature and moisture equilibrium with a
1.1 These definitions pertain to the conditioning of materials
standard atmosphere.
for test purposes. Unless otherwise specified, they are intended
conditioning—the exposure of a material to the influence of a
to apply to all cases where combinations of atmospheric
prescribed atmosphere for a stipulated period of time or until
influences are an essential part of the testing of materials.
a stipulated relation is reached between material and atmo-
1.2 It is the intent of this standard to include those condi-
sphere.
tioning terms in wide use in ASTM for which standard
dehumidify—to reduce, by any process, the quantity of water
definitions appear desirable.
vapor within a given space.
2. Referenced Documents dew point—the temperature to which water vapor must be
reduced to obtain saturation vapor pressure, that is, 100 %
2.1 ASTM Standards:
relative humidity.
E 171 Specification for Standard Atmospheres for Condi-
tioning and Testing Materials
NOTE 1—As air is cooled, the amount of water vapor that it can hold
E 337 Test Method for Measuring Humidity with a Psy-
decreases. If air is cooled sufficiently, the actual water vapor pressure
chrometer (the Measurement of Wet- and Dry-Bulb Tem- becomes equal to the saturation water-vapor pressure, and any further
cooling beyond this point will normally result in the condensation of
peratures)
moisture.
3. Terminology
humidify—to increase, by any process, the quantity of water
3.1 Definitions:
vapor within a given space.
humidistat—a regulatory device, activated by changes in
air conditioning—the simultaneous control of all, or at least
humidity, used for the automatic control of relative humidity.
the first three, of those factors affecting both the physical and
humidity—the condition of the atmosphere in respect to water
chemical conditions of the atmosphere within any structure.
vapor. (See also humidity, absolute; humidity, relative.)
These factors include temperature, humidity, motion, distri-
humidity, absolute—the weight of water vapor present in a
bution, dust, bacteria, odor, and toxic gases.
unit volume of air, for example, grains per cubic foot, or
air, dry—air containing no water vapor.
grams per cubic metre.
air, saturated—a mixture of dry air and water vapor in which
the latter is at its maximum concentration for the prevailing
NOTE 2—The amount of water vapor is also reported in terms of weight
temperature and pressure. per unit weight of dry air, for example, grains per pound of dry air. This
value differs from values calculated on a volume basis and should not be
atmospheric pressure—the pressure due to the weight of the
referred to as absolute humidity. It is designated as humidity ratio,
atmosphere. It is the pressure indicated by a barometer that
specific humidity, or moisture content, which also see.
registers actual atmospheric pressure which is not corrected
to sea level equivalence. Standard atmospheric pressure is a
humidity ratio—in a mixture of water vapor and air, the mass
pressure of 76 cm Hg (101325 Pa) having a density of
of water vapor per unit mass of dry air.
3 2
13.5951 g/cm , under standard gravity of 980.665 cm/s .
humidity, relative—the ratio of the actual pressure of existing
atmosphere, standard—air maintained at a specified tempera-
water vapor to the maximum possible (saturation) pressure
ture, relative humidity, and standard atmospheric pressure.
of water vapor in the atmosphere at the same temperature,
E 171
expressed as a percentage.
humidity, specific—in a mixture of water vapor and air, the
mass of water vapor per unit mass of moist air.
These definitions are under the jurisdiction of ASTM Committee G3 on
moisture content—the moisture present in a material, as
Durability of Nonmetallic Materials and are the direct responsibility of Subcom-
determined by definite prescribed methods, expressed as a
mittee G03.92 on Terminology.
percentage of the weight of the sample on either of the
Current edition approved
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