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, negative pressure fans are used to exhaust impure and hot air from indoors, while the water curtain wall opposite the fans is used for intake. Fresh, warm outdoor air, as it passes through the wet holes of the water curtain wall, undergoes heat exchange with the water, getting filtered and cooled.