An HVAC duct is a passageway that distributes heated or cooled air through a building. It is part of the heating, ventilation, and air conditioning system. The duct carries air from the furnace or air handler to the rooms, and from the rooms back to the unit. It is made of sheet metal, fiberglass, or flexible plastic. It is sealed to prevent leakage and insulated to prevent heat loss. The duct is the circulatory system of the building. In the kitchen, the equivalent is the range hood duct. It carries smoke, steam, and grease from the stove to the outside. It is a duct. It is an HVAC duct. It is the duct of the kitchen. It is the duct of the cook.

Ducts come in several types. A trunk duct is the main line. A branch duct serves a single room. A flexible duct is a corrugated tube that can be routed around obstacles. A rigid duct is made of sheet metal and is more efficient. The duct is sized based on the air volume and the static pressure. Too small, and the system cannot deliver enough air. Too large, and the air moves too slowly and does not mix. In the kitchen, the range hood duct must be sized for the exhaust. It must be short. It must be straight. It must be smooth. It must be sealed. It must be vented outside. The duct is the path. The path is the duct. The duct is the same.

Duct installation is a trade. The sheet metal worker fabricates and installs the duct. The duct must be sealed with mastic or tape. It must be insulated in unconditioned spaces. It must be supported at regular intervals. It must not be crushed or kinked. Leaky ducts waste energy and reduce comfort. In the kitchen, the range hood duct must be installed by a professional. It must be vented to the outside. It must not be vented into the attic. It must not be vented into the wall. It must be vented outside. The duct is the path. The path is the duct. The duct is the kitchen. The kitchen is the duct. The duct is the cook. The cook is the duct. The duct is the same. The same is the meal. The meal is the duct. The duct is the same.