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IAQ Glossary M


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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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