Axial roof ventilators are installed on the roof for exhaust and air exchange. Due to the uniqueness of the installation and usage environment, it determines the special materials and structure of the fan. Roof ventilators are equipped with a device to prevent reverse airflow after shutdown, as the fan rotates at high speed under the influence of thermal pressure, causing a significant increase in wind speed inside the wind tube. The reverse rotation of the fan is detrimental to the motor's start-up, which may damage the motor due to excessive starting current. Roof ventilators should be designed with reliable rainproof, snowproof, and windproof performance. Unlike rain, snow and sand can not only enter the fan from above but may also enter from below when the outdoor wind speed reaches a certain intensity.