Fume hood is a special form of airtight cover, can cause harmful actions process is carried out in a hood, ventilation Cabinet usually has a hole and hole opening and closing operations, in order to prevent fume hoods in the mechanical equipment of disturbance, chemical reactions or heat pressing causes of pest escape, fume hood must be ventilation, negative pressure within the Cabinet. Fume hood exhaust fan of many forms, usually applications are:
(1) upper exhaust fume hood. When fume hoods in the harmful gas denser than air is small, or when ventilation when heating element inside the Cabinet, to effectively prevent the escape of harmful gases from the upper edge of the operation, select the upper exhaust fume hood. This type of fume hood is simple in structure, wide range of applications.
(2) lower exhaust fume hoods. When the hood is no fever, and harmful gas denser than air, air flow in the Cabinet declined, to effectively prevent the escape of harmful gases from the operations under margin, lower exhaust fume hood should be chosen. This type of fume hood exhaust section seams close to the console, or from the console of a certain height.