In a closed factory space, negative pressure fan equipment is installed on the wall or roof to extract the hot and humid air in the factory and allow the cool air outside the factory to flow smoothly into the room, forming an in-and-out air flow called “negative pressure”. Through this system, heat, odor, and dust can be discharged outside the factory, accelerating air circulation. Yifeng negative pressure fans can effectively improve the heat and air quality in the factory, and improve the work efficiency and health of factory workers.