ABSTRACT
Local exhaust ventilation (LEV) describes an important approach for preventing contamination of workroom air. The LEV system withdraws the contaminant at its source into an exhaust system for discharge to the air cleaner or building exterior. The local exhaust hood is the point of air entry into the duct system and the term "hood" is used in a broad sense to include all suction openings regardless of their shape or their physical disposition. Enclosing hoods and booths are typified by the common laboratory hood or spray painting booth in which one face of an otherwise complete enclosure is open for access. Exterior hoods effect their local exhaust action by creating directional air currents adjacent to the suction opening. The design of an exterior hood involves specifying its shape and dimensions, its position relative to the evaporation or pulvation zone, and the rate of air exhaust. Exhausted Enclosures are some of the most important devices for the control of air contaminants.
