How Does an Air Duct System Work?

Air ducts are a collection of tubes that form the air distribution network of your HVAC system. Because residential ducts are mostly concealed, you may not know how the different parts work. Read today’s blog to learn the main components of the ductwork system and how they operate.

Ducts (Pipes and Trunks)

The duct pipes and trunks are the primary channels that provide a path for heated or cooled air to blow throughout your home. The duct pipes branch out from the duct trunk to the different rooms in your house. The duct trunk is the main duct from the furnace, usually made of steel. Notably, flexible aluminum (called flexible piping) can be used where your walls may require a bendable option.  

Duct Transitions

Air ducts should be connected according to the specific shape of your home. The pipes and trunks use duct transitions to connect. There are many types of duct transitions and specialized connectors that join to make paths for air to go through your home.


A plenum is a large container that stores air for your HVAC system and is attached to the various ducts. Usually, there are two plenums to your ductwork. Your HVAC system will fill the supply plenum with cooled or heated air, which is sent through the ductwork. As the cooled or heated air enters a room, it forces the existing air out into another group of ducts. These ducts transfer this returned air to the return plenum. Then, the returned air is directed outside through a flue or filtered and sent back through the system.   

Related Post: Superior Air Duct Looks at the History of HVAC Systems      


Flues remove the toxic gasses that were created through the heating and cooling process and bring the air outside.

Refrigerant Lines

The refrigerant lines bring refrigerant into the compressors, which allows your HVAC system to heat or cool your air. 

Air Handler

The air handler is where the filter and blower fan situate. The blower fan transports the air through the ductwork. The air handler may also include heating or cooling coils.  

Drain Pans and Lines 

While HVAC systems heat or cool the air, they typically dehumidify the air, too. During the heating and cooling process, condensation builds up within the system. It needs somewhere to go; otherwise, rust or mold can occur inside your home. Drain pans take this water that has been created and empty it using the drain lines outside of your home.  

 Related Post: Types of Duct Systems – Materials, Shapes, and More

Schedule Residential Air Duct Cleaning 

Now that you’re familiar with how a duct system works, it’s time to schedule residential air duct cleaning. With clean air ducts, you can experience healthy air quality and an efficient HVAC system. We are a NADCA certified company, and we provide visual proof of your clean ducts. Contact Superior Air Duct Cleaning in western Pennsylvania or eastern Ohio. We look forward to hearing from you!