Heating and aeration equipment, metal, Metal constructions for the building industry, Construction, Air inlets and outlets (registers), metal, for ventilation systems, Fans and ventilators, high efficiency, Heating, ventilation, air conditioning (HVAC) and refrigeration equipment, Dampers or regulators for ventilation systems, Fans and ventilators, variable-pitch (VP), variable speed, Blowers, medium pressure, Ventilation equipment