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IAQ Glossary P


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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 micrometers.

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 disease.

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 as seven.

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 standard.

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PESTICIDE: a chemical used to kill or control living organisms. Pesticides include insecticides, herbicides, fungicides, rodenticides, antimicrobial agents,
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 zone.

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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 chemisorption)

POTENTIATION: the process of causing more physiological activity.

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 its container.

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 at 32F.

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.

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 hydrostatic pressure.

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 to 20oC).

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 heat.

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