The classification of HVAC ducts can be carried out according to a number of criteria, and here's the detailed classification of HVAC ductwork by its use.

Supply Ducts:

1. Main Supply Duct: Connects to the air handling unit (AHU) or fan, responsible for distributing air to various branch ducts.

2. Branch Supply Duct: Branches off from the main supply duct to deliver air to specific rooms or areas.

3. Terminal Supply Duct: Closest to the supply outlet, often equipped with diffusers or air nozzles to distribute air into the indoor space.

Return Ducts:

1. Main Return Duct: Collects air from rooms or areas and directs it back to the air handling unit or fan.

2. Branch Return Duct: Branches off from the main return duct to collect air from specific areas.

3. Return Air Outlet: Located at the end of the return duct in a room or space, drawing indoor air into the return system.

Exhaust Ducts:

1. Main Exhaust Duct: Used to expel contaminated air or exhaust gases from a space, typically connected to the exhaust system’s main fan or processing unit.

2. Branch Exhaust Duct: Branches off from the main exhaust duct to expel gases or odors from specific areas.

3. Exhaust Air Outlet: Located at the end of the exhaust duct, used to expel gases or odors to the outdoors.

Fresh Air Ducts:

1. Main Fresh Air Duct: Brings fresh outdoor air into the building, usually connected to the fresh air processing unit or air handler.

2. Branch Fresh Air Duct: Branches off from the main fresh air duct to distribute fresh air to specific areas.

3. Fresh Air Outlet: Located at the end of the fresh air duct, bringing fresh outdoor air into the indoor space.

Smoke Exhaust Ducts (typically for specific applications):

1. Main Smoke Exhaust Duct: Used to expel smoke from a building during a fire or emergency, usually connected to the smoke exhaust fan.

2. Branch Smoke Exhaust Duct: Branches off from the main smoke exhaust duct to collect and expel smoke from different areas.

3. Smoke Exhaust Outlet: Located at the end of the smoke exhaust duct, expelling smoke to the outdoors.

Bathroom and Kitchen Exhaust Ducts:

1. Bathroom Exhaust Duct: Specifically used to expel moisture and odors from bathrooms, usually smaller and shorter.

2. Kitchen Exhaust Duct: Used to remove grease and odors from kitchens, typically requiring higher exhaust capacity and heat resistance.

Ventilation Ducts:

1. Ventilation Duct: Used to improve indoor air quality and enhance air circulation, but not specifically for supply or exhaust.

The design and layout of these ducts should be determined based on actual usage requirements, building structure, and system airflow needs to ensure efficient operation of the ventilation, air conditioning, and smoke control systems. If you have specific scenarios or need more detailed design advice, feel free to let me know!