Ventilation in HVAC systems refers to the duct work. This is the network of tunnels directing air into and out of rooms in a home or building. Commercial and residential systems differ in size and materials, but generally utilize the same design elements. There are three systems of these tunnels one that supplies treated air, one that returns air, and one for exhaust air. There are many different components within each duct to regulate flow and filter air. Below is a diagram of basic components duct work and descriptions of each part.


Supply Plenum: Delivers treated air into the supply duct from the air handler.

Return Air Drop: Brings air from inside the room to the air handler for treatment and redistribution.

Flared Rectangular Take-Off: Connects duct work to supply plenum.

Reducer: Tapered joint attached to main duct leading to a narrower duct.

Top Take-Off: Connects round branch lines to main duct.

Boots: Delivers treated air to a room and contains a register.

Stack Head: vertical connection boot to wall register.

Wall Stack: Vertical duct work inside a wall to a stack head.

Panning: Flat metal nailed to return air joists.

Outside Air: Duct attached to an outside vent to bring fresh air into the system.

Volume Control Damper: These are used to control the flow of air into and out of duct work.