The local exhaust of the fume hood is a local ventilation method that directly removes pollutants from the source of the pollutants. When pollutants are concentrated somewhere, local exhaust is a very effective ventilation method to control the harm of pollutants to the environment. If ventilation is used in this situation, it will cause the pollutants to spread indoors; when the amount of pollutants is large, the required dilution ventilation volume will be too large, and even difficult to achieve in practice. There are many specific situations where pollutants occur in industrial plants, such as electroplating tanks, blanking points or operating points conveyed by bulk belts, welding workbenches, chemical analysis benches, spray paint, grinders, etc. There are also some specific situations that generate pollutants in civil buildings, such as stoves in kitchens, hot pots in restaurants, chemical test benches in schools, etc. It can be seen that local exhaust has a wide range of applications.  

        If the fume hood is placed in an air-conditioned, purified or heated room, in order to reduce the exhaust volume of indoor air, an air curtain can be installed above the cabinet door. The air sent out by the air curtain can be taken from the outdoors or an adjacent room, and the air volume is about 70% to 75% of the exhaust volume. This type of fume hood is called a supplied air fume hood. It can not only avoid the interference of indoor lateral airflow, but also save indoor exhaust air volume, greatly reducing indoor heat and cooling losses.
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