The basic function of the fume hood is, of course, to maintain ventilation. It is an exhaust device that can achieve a partial exhaust effect. And its exhaust air volume is variable, mainly in the following points:
The window of the staff room in the laboratory is likely to change, and in order to keep the wind speed stable, the air volume must adapt to the height of the window of the staff room, which needs to be changed with the height of the observation. Therefore, requiring the air volume to be variable is itself a kind of protection for the staff, and it is also a basis for the normal operation of the experiment.
In addition, many different experiments will be conducted in the same laboratory, and the accuracy of some experiments may be affected by the air volume. Of course, different experiments may have different requirements for air volume. Therefore, the air volume of the fume hood is variable, of course, to adapt to other uses.
Here, there is another point that we need to explain. The main reason why the fume hood can play a variable role is that the current equipment has a reasonable air volume control system. And this control system can issue different commands according to the different requirements of the laboratory for air volume, which is in line with the effect of the variable.