http://www.vent-axia.com/range/hr500-hr500x.html
Vent Axia HR500 and HR500X Single Room Heat Recovery Units
Heat recovery ventilation unit for through the wall installation which exhausts stale air whilst introducing warmed fresh air from the outside. As a heat recovery ventilation unit it moves a useful 550m³/h of air. This unit is fully speed controllable with the facility to reverse the supply air fan and provide 'double extraction' for periods when heat loss is desirable.
The unit is the perfect solution to commercial areas that require a high performance balanced intake/extract scheme. Ideal for swimming pools, computer rooms, classrooms, offices and the health and leisure industries. In noise sensitive areas use an auto transformer controller.