Particulate Matter

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

Particulates

Fine liquid or solid particles such as dust, smoke, mist, fumes, and fog found in air and emissions.

Parting Stop

A narrow strip, either integral or applied, that holds a sash or panel in position in a frame.

Pascal's Law

A pressure imposed upon a fluid is transmitted equally in all directions.

Passive Adsorption

A process by which a gas or vapor is condensed (out of the air) and held on the surface of a piece of solid material by natural forces only.

Passive Smoker

A non smoker who shares the same room, building, or space as a smoker, and thus is exposed to the products of tobacco combustion.

Patio

A courtyard an open paved area used for outdoor living and which may or may not be partially or entirely surrounded by rooms or other parts of a house.

Payback Analysis OR Return on Investment

Overall measure of the efficiency and value of your home comfort system. By combining your purchase price and ongoing operating costs, a payback analysis determines the number of years required before monthly energy savings offset the purchase price.

Peak Load

The maximum thermal load to be provided by a heating or cooling system in a house.

Peletier Effect

When direct current is passes through two adjacent metals one junction will become warmer. This principle is the basis of thermoelectric refrigeration.

Penetrating Oil

Oil used to loosen joints- particularly rusted ones- between metal parts.

Penthouse

A building on the roof of a structure that contains elevator machinery, ventilating equipment, etc, separate dwelling or apartment on the roof of an apartment house or other building any roof-like shelter or overhanging part, e.g., a part that shelters a doorway.

Perception

Awareness of the effects of stimuli.

Perimeter

The total length of the periphery of a given area e.g., the distance around the outside of a building.

Permanent Incorporation

When referring to wood framing members, this occurs when the wood is cut to size and nailed in place.

Permanent Magnet

A material which has its molecules aligned and has its own magnetic field bar of metal which has been permanently magnetized.

Perpendicular

Being at right angles (90 degrees) to a given line, plane or surface.

Photochromics

Glazing with the optical properties that change in response to the amount of incident light.

Photoelectricity

A physical action wherein an electrical flow is generated by light waves.

Picture Window

A large window, usually a fixed pane of plate or insulating glass sometimes divided into small panes designed to command an interesting view or allow more light into the interior of the building.

Picture Window

A large, fixed window framed so that it is usually, but not always, longer horizontally than vertically to provide a panoramic view.

Pier

A masonry column, usually rectangular in horizontal cross-section, used to support other structural members.

Pigtail

(1) A flexible conductor attached to an electrical fixture which provides a means of connecting the fixture of a circuit. (2) A short length of copper conductor that is attached to the end of an aluminum branch circuit by a special fastener. The copper conductor is then fastened to the terminal of a switch or outlet.

Pilot Flame

Small gas flame or electric spark that ignites a gas burner in a range, waterheater, dryer, furnace or boiler.

Pilot Hole

Starter hole drilled into wood or metal before inserting a screw or nail to prevent fastener from splitting wood. Diameter of hole must be smaller than fastener.

Pilot Orifice

Small hole in a pilot through which gas passes before igniting.

Pinch-Off Tool

A device used to press walls of a tubing together until fluid flow ceases.

Piston

A close fitting part which moves up and down in a cylinder.

Piston Displacement

A volume displaced by piston as it travels length of stroke.

Pitch

The degree of roof incline expressed as the ratio of the rise, in feet, to the span, in feet.

Pivot Window

A window with a sash that swings open or shut by revolving on pivots at either side of the sash or at top and bottom.

Plant Component

Device within a plant network such as a boiler or pump.

Plastic Film

A thin plastic substrate, sometimes used as the inner layers in a triple- or quadruple-glazed window.

Plastics

Artificial substances made of organic polymers that can be extruded or molded into various shapes including window frames and sashes.

Plate Exchanger

A heat exchanger used to create free cooling (not using a compressor or refrigerant to transfer heat) by running colder tower water over stainless steel plates which transfers heat between the closed loop to the open loop.

Plate Glass

A rolled, ground, and polished product with true flat parallel plane surfaces affording excellent vision. It has been replaced by float glass.

Plenum

A chamber or large duct above a furnace that serves as a distribution area.  Air compartment connected to a duct or ducts.

Plenum Chamber

A chamber, at higher/lower pressure than surrounding air, which receives air before/after delivery to a conditioned space or combustion system.

Plumb

To determine if a vertical surface is exactly perpendicular (90 deg) to a horizontal plane.

Plume

A visible or measurable discharge of a contaminant body from a given point of origin. Can be a visible body of pollution such as smoke coming from a stack or a measured amount such as the heat in water coming from a power plant boiler.

Ply

A term to denote the number of sheets in a layered construction, such as plywood, roofing, filters, electrical wiring etc.

Pneumatic Controller

A controller, which uses compressed air as the control medium. All the required control terms are readily available, e.g., step control, etc.

Pollutant Migration

The movement of indoor air pollutants throughout the building between rooms or zones. The concentration within a given portion of air of harmful or unpleasant contaminants such as noxious gases or dust particles. Concentrations are often expressed as time weighted values over 24 hours, a working day or a working week.