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
MANOMETER: An instrument for measuring pressures:
especially a U-tube partially filled with a liquid,
usually water, mercury, or light oil, so constructed
that the amount of displacement of the liquid
indicates the pressure being exerted on the instrument.
MASS: The quantity of matter in a body as measured
by the ratio of the force required to produce
given acceleration, to the acceleration.
MEAN RADIANT TEMPERATURE: The uniform surface
temperature of a radiantly black enclosure in
which an occupant would exchange the same amount
of radiant heat as in the actual nonuniform space.
MEDIUM: A nutrient-containing substance used
for the growth and multiplication of microorganisms.
MESOPHILE: An organism that grows optimally within
the temperature range of 77oF to 104oF (25oC to
40oC).
METABOLIC RATE: Rate of energy production of
the body. Metabolism, which varies with activity,
is expressed in met units in this Standard. One
met is defined as 18.4 BTU/h ft2 (58.2 W/m2) which
is equal to the energy produced per unit surface
area of a seated person at rest. The surface area
of an average man is about 19 ft2 (1.8 m2).
MICROMETER (um): A unit of length that is 1/1X106
of a meter.
MICRON: A unit of length, the thousandth part
of 1 mm of the millionth of a meter.
MICROORGANISM: A minute organism; microbes, bacteria,
cocci, viruses, molds, etc., are microorganisms.
MILLIGRAM (mg): A unit of weight in the metric
system. One thousand milligrams equal one gram.
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MILLIGRAMS PER CUBIC METER (mg/m³): Unit
used to measure air concentrations of dusts, gases,
mists, and fumes.
MILLILITER (mL): A metric unit used to measure
volume. One milliliter equals one cubic centimeter.
MINIMUM TRANSPORT VELOCITY, MTV: The minimum
velocity which will transport particles in a duct
with little settling; the MTV varies with air
density, particulate loading, and other factors.
MIXED AIR: The part of an HVAC system where the
return air (RA) is mixed with the outside air
(OF); the air resulting from this mixing.
MODULATE: To control a damper or valve so that
it may assume any position between full open and
full closed, as well as these two positions.
MODULATION: Of a control, tending to adjust by
increments and decrements.
MODULATING CONTROL: A mode of automatic control
in which the action of the final control element
is proportional to the deviation, from set point,
of the controlled medium.
MODULATING CONTROLLERS: Constantly reposition
themselves in proportion to the requirements of
the system, theoretically being able to maintain
an accurately constant condition.
MOLD: (1) A growth of fungi forming a furry patch,
as on stale bread or cheese. See spore. A hollow
form or matrix into which molten material is poured
to produce a cast.
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MSDS: Material Safety Data Sheet
MUCOUS MEMBRANES: Lining of the hollow organs
of the body, notably the nose, mouth, stomach,
intestines, bronchial tubes, and urinary tract.
MULTIZONE: An HVAC system supplying air to two
or more locations, each location having its own
thermostat. The thermostat controls the delivered
air temperature by controlling damper positions
connected to a hot deck/cold deck.
MULTISTAGE THERMOSTAT: A thermostat which controls
multiple stages of auxiliary equipment for heating
or cooling in response to a greater demand for
heating or cooling.
MUTAGEN: Any chemical or physical agent that
causes a gene change (mutation) or speeds up the
rate of mutation.
MUTAGENIC AGENT: Any chemical substance or physical
agent that iscapable of enhancing the frequency
of detectable mutants within a population of organisms.
MUTATION: A sudden, usually rare, change in the
genetic code of an organism and results in a change
in function that is inheritable.
MYCOVIRUS: Viruses with a host-range specificity
limited to the fungi.
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