Generally, the horizontal flow purification workbench adopts the open-loop mode. This mode of purification workbench has a simple structure and low cost, but the load of the fan and the filter is relatively large, which will adversely affect its life. The closed-loop mode is actually not a completely closed air circulation. In each cycle, some air is discharged into the ambient space, but these discharged gases have been filtered by an external high-efficiency air filter.