Ducting is used to deliver and remove air, to and from a building. A duct is a type of conduit that is used for applications such as heating or ventilation. The scalability can differ from being used in a simple extractor fan cooker design, all the way up to a large factory. They facilitate the needed airflow, such as return air, exhaust air and supply air. More often than not, ducts also deliver ventilation air as part of a supply air application.