It is a ventilation fan with a two-way linkage. It can also expel heated air masses and draw in cold natural wind to provide ventilation in addition to removing smoke. High-quality, steady, quiet, wear-resistant sleeve bearing motor. Easy operation with overheat protection, effective temperature fuses, and safer operation On the initial pull, the fan activates and vents upward. On the second pull, the fan operates in reverse and blows air inward. The third pull will cause the louver to close and the ventilation fan to turn off.