In recent years the efficiency of ERUs has improved dramatically and their costs have dropped thanks to mass production. The wheel rotates from the exhaust air stream to the incoming supply air stream. Thus, on cold days, the incoming air is heated, on hot days it is cooled. With energy recovery efficiencies of seventy to eighty percent, such systems substantially reduce the operating cost of ventilation in the designated smoking areas. Lounge - Transfer Air Every building is by law equipped with toilets.
All toilets have to be equipped with exhaust ventilation to remove odours, germs, etc.
To ensure ease of operation, it is usual to fit such toilets with exhaust systems only. Each draws its supply air from adjacent areas. Corridors, offices, etc. Therefore, the suction of air from the restroom creates a negative pressure in the restroom relative to the adjoining areas. Air, like water always flows from a high pressure area to a low pressure area.