Water curtain walls, also known as wet curtain walls, consist of water curtain panels and frames, commonly used in negative pressure ventilation and cooling systems. In negative pressure ventilation and cooling systems, a negative pressure fan is used to exhaust polluted and hot air from the interior, while the water curtain wall opposite the fan is used for intake. Fresh, hot outdoor air is cooled and filtered as it passes through the wet holes of the water curtain wall, undergoing a heat exchange with the water.