Usually round or rectangular metal pipes installed for distributing warm or cold air from the heating and air-conditioning equipment.

Ducts are large diameter conduits, that deliver heated/cooled air throughout the house. Older houses have ducts made from sheet metal, but today, ducts are usually insulated, flexible plastic tubes.

Metal, vinyl, or insulated foam-board pipes, usually rectangular, which carry forced warm air from the heating unit to various parts of the house; also used to circulate cooled air from the air-conditioning unit.

Large pipes used to distribute air from a central heating or air conditioning system.

underground pipes through which telecom cables are laid.

The heating system. Usually round or rectangular metal pipes installed for distributing warm (or cold) air from the furnace to rooms in the home; also a tunnel made of galvanized metal or rigid fiberglass, which carries air from the heater or ventilation opening to the rooms in a building

are round or rectangular metal pipes used for distributing warm or cold air from heating and/or air conditioning systems.

Large pipes for air, used in central air conditioning and heating systems.

Pipe that carries water, cooled air or wiring throughout a house.

The round or rectangular pipes found in most homes connected to the heating/cooling system for distributing warm or cool air throughout the home.