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
PARADICHLOROBENZENE: a chemical ingredient in
mothballs and certain deodorizer products, currently
regarded as a possible carcinogen by NIOSH; p-dichlorobenzene.
PARTICULATE: A state of matter in which solid
or liquid substances exist in the form of aggregated
molecules or particles. Airborne particulate matter
is typically in the size range of 0.01 to 100
PARTICULATE MATTER: A suspension of fine solid
or liquid particles in air, such as dust, fog,
fume, mist, smoke, or sprays. Particulate matter
suspended in air is commonly known as an aerosol.
PASSIVE SMOKING: the inhalation of environmental
tobacco smoke; also called involuntary smoking.
PATHOGEN: Any microorganism capable of causing
PATHOGENIC: Having the ability to produce or
cause a disease.
pH: Means used to express the degree of acidity
or alkalinity of a solution with neutrality indicated
PENICILLIUM: a genus of fungi found in indoor
air. plant materials, and wet insulation, which
has been associated with hypersensitivity pneumonitis
in susceptible individuals.
PERCUTANEOUS: occurring through the skin (as
in percutaneous absorption)
PERMEABLE: porous, allowing the passage of air.
PERMISSABLE EXPOSURE LIMIT (PEL): An exposure
limit is published and enforced by OSHA as legal
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PESTICIDE: a chemical used to kill or control
living organisms. Pesticides include insecticides,
herbicides, fungicides, rodenticides, antimicrobial
and plant growth regulators.
PHARYNX: the region of the human respiratory
system tract where the nasal passage joins with
the food passage.
PHENOLIC RESINS: A class of resins produced as
the condensation product of phenol or substituted
phenol and formaldehyde or other aldehydes.
PICKUP: The temperature increase across a coil.
PITOT TUBE: A device consisting of two concentric
tubes, one serving to measure the total or impact
pressure existing in the air stream, the other
to measure the static pressure only.
PLANE RADIANT TEMPERATURE: The uniform temperature
of an enclosure in which the incident radiant
flux on one side of a small plane element is the
same as in the existing environment.
PLENUM: the portion of the air distribution system
that makes use of the building structure, and
the sheet metal that connects distribution ductwork
to an air handling unit. Many buildings use the
space above a dropped ceiling as a plenum.
PLUG FLOW: a type of airflow whereby supply air
moves in one direction from supply to exhaust,
sweeping contaminants from workspace or breathing
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PNEUMONIA: A swelling of the lungs, commonly
caused by breathed-in bacteria (Diplococcus pneumoniae).
Parts of the lungs become plugged with a fiber
like fluid. Virus rickettsiae, and fungi may also
cause pneumonia. Symptoms of pneumonia are severe
chills, a high fever (which may reach 105oF),
headache, cough, and chronic pain. An involved
lower lobe of the right lung may cause a pain
that is like appendicitis. Red blood cells leaking
into the air sacs of the lungs causes a rust-colored
sputum that may be a sure sign of pneumococcal
infection. The disease continues, sputum may become
thicker and have pus. The patient may have painful
attacks of coughing. Breathing often becomes painful,
shallow, and rapid. The pulse rate goes up, often
over 120 beats a minute. Other signs may be heavy
sweating and bluish skin. Stomach and bowel disorders
and an outbreak of shingles (herpes simplex) on
the face may also occur. Children with pneumonia
may have seizures. The affected area of a lobe
becomes filled with fluids and firm. The physician
hears a distinct breathing sound. X-ray films
are taken of the lungs. Laboratory tests of sputum
and blood help in finding the cause.
POINT OF OPERATION: Used to designate the single
set fan performance values which correspond to
the point of intersection of the system curve
and the fan pressure-volume curve.
POLAR COMPOUNDS: chemical compounds that have
equally strong positive and negative charged on
opposite ends of its molecular structures, e.g.,
alcohols and ketones.
POLLUTANT: a contaminant known to cause illness.
POLYCYCKLIC AROMATIC HYDROCARBONS (PAH): a group
of complex organic substances generally associated
with certain combustion processes, such as tobacco
smoking, wood burning, and cooking. Health effects
attributed to PAHs include cardiovascular effects
and irritation. The US EPA classifies four PAH
compounds as Group B2 probable carcinogens: benz(a)anthracene,
benzo(a)pyrene, debenzo(a,h)anthracene, and 3-methylcholanthrene.
POTABLE WATER: Water that is safe for human consumption.
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POTASSIUM PERMANGANATE (KMnO4): an oxidizing
agent impregnated on activated alumina (used in
POTENTIATION: the process of causing more physiological
POWER (P): Expressed in watts (W) or kilowatts
(kW), and is equal to:
in DC circuit, P = EI and P = I2R
in AC circuit, P = EI X Power factor
PPM: parts per million.
PREHEAT: A coil used to raise the outside air
temperature above freezing, generally to 35oF.;
the process of raising the temperature.
PRESSURE: The normal force exerted by a homogeneous
liquid or gas, per unit of area, on the wall of
PRESSURE, ABSOLUTE: Pressure referred to that
of a perfect vacuum. It is the sum of gauge pressure
and atmospheric pressure.
PRESSURE, ATMOSPHERIC: It is the pressure indicated
by a barometer. Standard atmosphere is the pressure
equivalent of 14.697 psi or 29.921 in. of mercury
PRESURE DIFFERENTIAL: the difference between
air pressures measures at two locations.
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PRESSURE DROP: Pressure loss in fluid pressure,
as from one end of a duct to the other, due to
friction, dynamic losses, and changes in velocity
PRESSURE, GAUGE: Pressure above atmospheric.
PRESSURE LOSS: The term used in the register
industry to indicate how much total pressure is
required to move air through a register.
PRESSURE MAINTENANCE: a program of building maintenance
implemented to reduce the possibility of IAQ problems,
usually through periodic inspection, cleaning,
adjustment, calibration, and replacement of functioning
parts of the HVAC system, as well as housekeeping
practices to reduce the buildup of potential contaminants.
PRESSURE, SATURATION: The saturation pressure
for a pure substance for any given temperature
is that pressure at which vapor and liquid, or
vapor and solid, can coexist in stable equilibrium.
PRESSURE, STATIC (SP): The normal force per unit
area that would be exerted by a moving fluid on
a small body immersed in it if the body were carried
along with the fluid. Practically, it is the normal
force per unit are at a small hole in a wall of
the duct through which the fluid flows (piezometer)
or on the surface of a stationary tube at a point
where the disturbances, created by inserting the
tube, cancel. It is supposed that the thermodynamic
properties of a moving fluid depend on static
pressure in exactly the same manner as those of
the same fluid at rest depend upon its uniform
PRESSURE, TOTAL (TP): In the theory of the flow
of fluids, the sum of the static pressure and
the velocity pressure at the point of measurement.
Also called dynamic pressure.
PRESSURE, VAPOR: The pressure exerted by a vapor.
If a vapor is kept in confinement over its liquid
so that the vapor can accumulate above the liquid,
the temperature being held constant, the vapor pressure approaches a fixed limit called
the maximum, or saturated, vapor pressure, dependent
only on the temperature and the liquid.
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PRESSURE, VELOCITY (VP): In moving fluid, the
pressure capable of causing an equivalent velocity,
if applied to move the same fluid through an orifice
such that all pressure energy expended is converted
into kinetic energy.
PRIMARY AIR: The initial air stream discharged
by an air outlet (the air being supplied by a
fan or supply duct) prior to any entrainment of
the ambient air.
PSYCHROMETER: An instrument for ascertaining
the humidity or hygrometric state of the atmosphere.
PSYCHROMETRIC CHART: A graphical representation
of the thermodynamic properties of moist air.
PSYCHROPHILE: An organism that grows optimally
within the temperature range of 32oF to 68oF (0oC
PSYCHOGENIC: originating in the mind or in mental
or emotional conflict.
PULMONARY: having to do with that part of the
lungs where gas exchange occurs, including the
alveolar ducts and alveoli.
PULMONARY EDEMA: an accumulation of fluid in
the pulmonary region of the lungs.
PURE CULTURE: A culture of microorganisms in
which all cells are of a single type.
PURPURA: a hemorrhagic state characterized by
eruption of blood vessels into the skin and mucous
membranes resulting in patches of purplish discoloration.
PYROLYSIS: the chemical decomposition or other
chemical changes brought about by the action of
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