Adopt front double door opening mechanism, small wind resistance, good closure, high efficiency; The air duct adopts plug-type linkage mechanism, which avoids the cumbersome fastening of bolts and nuts, reduces the labor intensity of heating, and improves the appearance of the fan. Rubber sealing device is added when the fan doors are closed. When multiple fans are started at the same time according to the environmental conditions, it can effectively avoid outdoor air entering from other stop fans, greatly improve the working efficiency of the fan and ensure that the air enters through the wet curtain or ventilation window (compared with fans of the same size, the efficiency can be improved by 15-20%).