Canopy Hood
An extraction hood: a skirt round a rectangular opening, four sloping sides and a collar for the duct, in the middle or against a wall. An extraction hood: an upright skirt round a rectangular opening, four sloping sides and an upright collar for the duct, with the collar in the middle or against a wall.
How the canopy hood is developed, with a worked example · Hoods, plenums and cyclones