This topic covers information related to diffusers, registers and grilles installed as part of HVAC systems during construction. Diffusers, registers and grilles are finish elements of an HVAC system where air is supplied or removed from a space or building.

This topic covers information related to air terminal units installed as part of HVAC systems during construction. Air terminal units control or modify the amount and temperature of air being distributed to a specific zone in order to achieve a desired comfort level within the space. Air terminal units are either a constant or variable volume systems.

This topic covers information related to HVAC fans installed as part of HVAC systems during construction. HVAC fans can be one of several types; axial, centrifugal, power ventilators or air curtains. Axial fans in construction are commonly known as ceiling fans. Centrifugal fans are commonly found in mechanical units that distribute air. Power ventilators are used to draw air from a room or portion of a structure and remove heat and/or moisture, such as attic vents and gable vents. Air curtains are stand alone devices that generate a wall of air that separates two spaces, such as an entry from the outdoors to the indoors.

This topic covers information related to flexible ducts installed as part of HVAC systems during construction. Flexible ducts are round in shape and can be made from plastic with glass wool insulation over metal coiled wire.

This topic covers information related to dampers installed as part of HVAC systems during construction. Volume control dampers can be installed inside a duct or as part of a register or diffuser. They are adjustable devices that control the volume of air provided to a specific location within a structure. Smoke and fire dampers are installed inside a duct located in a firewall. They are automated devices that close to prevent the spread of fire.

This topic covers information related to testing, adjusting and balancing of heating, ventilation and air conditioning (HVAC) systems installed during construction. Testing evaluates HVAC equipment, adjusting sets devices within an HVAC system to achieve efficient performance during operation and balancing is performed to regulate air or water flow of an HVAC system.

Fire is a chemical chain reaction. Molecules of a flammable material contain stored energy. When they are heated to a certain point, they react with oxygen, releasing that energy in the form of heat. This heat energy then causes other nearby flammable molecules to react with oxygen, continuing the cycle. Fire needs the heat, oxygen, and a fuel of flammable material to continue burning. Fire-extinguishing systems work by separating one or more of the key elements from the equation. Fire is impossible without oxygen. Likewise, if there is no heat, fire cannot spread. And, obviously, if there is no fuel, there is nothing to burn.

Wet-pipe sprinkler systems are the most common fire suppression systems.  In a wet-pipe system, either the water supplied by the municipality or the water supplied from a fire pumping station provides constant pressure for the system.  When a sprinkler in this system is activated through melting of its fusible link, water is immediately discharged onto the fire.  Water will flow until the fire is extinguished and until the fire marshal shuts off the water supply.