Principle of Heat Exhaust
When the negative pressure ventilation fan operated, the indoor hot air was enforced to exhaust. Meanwhile, the air from outside was pull in from gates or windows to fill the room. Accordingly the flowing air lower the indoor temperature as well as brings fresher air.
Normally all the fans installed on opposite side of doors or windows of factory, which is favorable for people inside the factory to feel the air flow when the negative pressure ventilation fan was operated.