Combined ventilation device for cable trench

A combined ventilation device for a cable trench relates to the field of power equipment. According to the utility model, the problems of high labor intensity, low safety coefficient and potential safety hazard when workers enter the trench for detection due to the fact that harmful substances are generated in the trench and the ventilation effect is poor because the interior of the existing transformer substation cable trench is sealed for a long time are solved. One end of a cylindrical fan body is provided with a combined support, the other end of the cylindrical fan body is sleeved with a hose body, the hose body is connected with an air outlet of the cylindrical fan body through a hoop, and the end, away from the cylindrical fan body, of the hose body is provided with four first semicircular rings. The hose body is connected with the foldable support through four first semicircular rings, the other first semicircular ring is fixed to the inner wall, close to a port, of the hose body, a harmful gas detect