HVAC GLOSSARY - P

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Package Unit or Package System: A self-contained unit or system that has the Air Handler & Condenser in same unit. Normally placed outside the home and connected to a duct system by penetration through the home’s foundation. Except for geothermal which is a self-contained indoor unit that is placed in a closet, attached garage, basement, or mechanical room.

PAPR: Powered air purifying respirator.

Particulates: Small airborne particles found in indoor environments which include fibrous materials, solid-state semi-volatile organic compounds, and biological materials.

Pascals: (Pa) A small unit of air pressure. One pound per square inch equals 6,895 pascals.

Passive Smoking: The inhalation of environmental tobacco smoke; also called involuntary smoking.

Pathogen: Any microorganism or substance that causes disease.

PELs: Permissible Exposure Limits (standards set by the Occupational, Safety and Health Administration).

Permeable: Porous, allowing the passage of air.

Personal Protective Equipment:(PPE).

Pesticides: Pesticides are chemicals that are used to kill or control pests which include bacteria, fungi, weeds, and other organisms, in addition to insects and rodents. Most pesticides are inherently toxic. Most contain volatile organic compounds.

Picocurie: A unit of measurement used to describe radon concentration.

Plenum: Air compartment connected to a duct or ducts. Air flow passage made of duct board, metal, drywall, or wood. Joins supply and return ducts with HVAC equipment. The portions of the air distribution system that makes use of the building structure, and the sheet meal that connects distribution ductwork to an air handling unit. Many buildings use the space above a dropped ceiling as a plenum.

Pollutant Pathways: Avenues for distribution of pollutants in a building. HVAC systems are the primary pathways in most buildings; however, all building components interact to affect how air movement distributes pollutants.

Positive Pressure: Condition that exists when more air is supplied to a space than is exhausted, so the air pressure within that space is greater than that in surrounding areas. Under this condition, if an opening exists, air will flow from the positively pressurized space, outward to surrounding areas.

Power: The rate at which energy is transferred. Electricity for use as energy is also referred to as power. Electrical power is usually measured in watts. Also used for a measurement of capacity.

PPM: (Parts Per Million) A unit, which may be mass/mass, and hence represents a direct measure of fractional mass, or volume/volume, and represents in this case, a molar fraction at low pressures and high temperatures, commonly used to represent the degree of pollutant concentration where the concentrations are small.

Pressed Wood Products: A group of materials used in building and furniture construction that are made from wood veneers, particles, or fibers bonded together with an adhesive under heat and pressure.

Pressure balancing: The process of neutralizing pressure differences within a home.

Preventive Maintenance:(PM) A program of building maintenance implemented to reduce the possibility of 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. Primarily done on a building's mechanical systems, this involves a regular and systematic inspection, cleaning, and replacement of worn parts, materials, and systems. Preventive maintenance helps to prevent parts, material, and systems failure by ensuring that parts, materials, and systems are in good working order.

Price of Quality: There is more to buying a heat pump or air conditioner than ratings. The quality of construction and materials used as well as the reliability of the manufacturer and installation contractor can all affect your long-term satisfaction and comfort. Top quality, high efficiency equipment will cost more initially, but it will save you money on utility bills and service calls for years to come. Be sure to weigh all the factors before choosing your new system.

Primary Air Flow Rate: Volume of air entering a supply air terminal device within a time unit.

Process Heating: Energy Efficiency program promotion of increased electric energy efficiency applications in industrial process heating.

Programmable Controller: A device that controls the operation of electrical equipment (such as air conditioning units and lights) according to a preset time schedule. 

Psychosocial Factors: Psychological, organizational, and personal stressors that could produce symptoms similar to those caused by poor indoor air quality.