Gravity ventilators use gravity ventilation, or natural ventilation. They require no power, motors, or fans to function. Air movement is achieved via the pressure differential between the inside and outside of the structure or building. This allows the intake and exhaust of air naturally. They are mainly used in buildings with open floor plans that do not require air conditioning. Specifications are mainly for heat removal and/or contaminant dilution. Gravity ventilation is achieved in buildings that are designed with spaced openings to best take advantage of wind patterns as well as thermal buoyancy or the ‘stack effect’. Also note that gravity ventilators may also be used in conjunction with powered ventilation systems.