The exhaust system of the Laboratory Fume Hood can be divided into two types: Chinese and distributed. A centralized system of ventilation cabinets of one floor or several floors, or the entire experimental building, into one or two systems. It is characterized by the lack of ventilation cabinets, equipment investment, and a slight increase in the number of ventilation cabinets, as well as the change of position, with certain adaptability. However, due to the large system, the air volume is not suitable for balance. Although the regulating valve is installed on each ventilation cabinet, it is not convenient to use, and it is not easy to achieve the intended effect. If the system duct damage needs to be overhauled, the whole system's Laboratory Fume Hood can not be used. So, the original centralized system of the laboratory, has switched to a decentralized system.
The distributed type is a ventilation cabinet or a few ventilation cabinets in the room into a ventilation system. Its characteristic is can according to the work of the Laboratory Fume Hood to be able to hit open and closed fume cupboard, mutual undisturbed, easy reach predetermined effect, and save energy than centralized type. Because the system is small and the exhaust volume is small, the air volume and wind pressure of the Laboratory Fume Hood are not large, and the noise is less vibration. Another characteristic of dispersion is that it is easy to dispose of harmful gases with different properties. The disadvantage is that the number of the ventilator, system, if the fan inside the ventilator room, then investment will increase, if the ventilator scattered layout, and on-site installation, although the ventilator increased investment in duct can save investment, total investment does not necessarily increase in the end. When dividing the system, if there are two or more Laboratory Fume Hoods in the same room, it should be classified as a system to avoid the use of a Laboratory Fume Hood, and the other fume cupboard can produce backflow.
Exhaust fan system, generally installed on the roof or top floor of the ventilator room so don't occupy usable floor area, and make indoor exhaust pipe is in negative pressure condition, lest because the harmful material pipe is not tight into indoor. In addition, the ventilator is installed on the roof or the top of the ventilation cabinet room, easy to repair, easy to reduce noise and vibration.