Glossary

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.

Plenum

HVAC term for an air compartment connected to a duct or ducts. 

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 into surrounding areas. 

Pressure, Static

In flowing air, the total pressure minus velocity pressure. The portion of the pressure that pushes equally in all directions. 

Pressure, Total

In flowing air, the sum of the static pressure and the velocity pressure. 

Pressure, Velocity

In flowing air, the pressure due to the velocity and density of the air. 

Preventative Maintenance

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. 

Programmable Thermostat

A type of thermostat that allows the user to program into the devices’ memory a pre-set schedule of times (when certain temperatures occur) to turn on HVAC equipment. 

Propane

A hydrocarbon gas, C3H8, occurring in crude oil, natural gas, and refinery cracking gas. It is used as a fuel, a solvent, and a refrigerant. Propane liquefies under pressure and is the major component of liquefied petroleum gas (LPG).