Any tube or canal by which a fluid or other substance is conducted or conveyed.
One of the vessels of an animal body by which the products of glandular secretion are conveyed to their destination.
A channel or passage through which fluids move.
sheet-metal tube used for air distribution.
A horizontal layer in the atmosphere in which temperature and moisture gradients are such that electromagnetic energy traveling within the layer is bent towards the earth's surface with a curvature equal to or greater than the earth's true curvature. A strong temperature inversion and/or moisture lapse rate are necessary for the formation of a duct.
A layer in the ocean where refraction and probably reflection result in the trapping of sound waves.
Applied to the atmosphere and ocean, any region with vertically varying properties such that waves of any kind (e.g., electromagnetic and acoustic) launched in certain directions are guided by or trapped within the region rather than propagating radially from their source. For a duct to exist, attenuation must be negligible over distances comparable to the characteristic linear dimensions of the duct.
A duct or ductwork used for the distribution or extraction of air, designed and tested to satisfy the criteria defined in BS 476: Part 24. (ISO 6944).
A fire resisting smoke outlet duct, for the extraction of products of combustion, designed and tested to satisfy the criteria defined in BS 476: Part 24. (ISO 6944). A smoke outlet duct must retain at least 75% of its cross-sectional area throughout the test.
A duct or ductwork that is installed entirely independent of any other duct or ductwork within the building and which serves as an extract for non-domestic kitchens (see clause 9.5 of BS 5588: Part 9), designed and tested to satisfy the criteria defined in BS 476: Part 24. (ISO6944).