11 EXHAUST HOODS FOR LABORATORY, INDUSTRIAL AND COMMERCIAL COOKING (AS DISTINGUISHED FROM "KITCHEN") PURPOSES; DUST, LIQUID DROPS AND PARTICLE COLLECTORS, GAS SCRUBBERS, ABSORPTION SCRUBBERS; HEAT EXCHANGERS; AIR HANDLING UNITS, AIR DISPLACEMENT VENTILATION UNITS, VENTILATING LOUVER DAMPERS, SUPPLY AIR GRILLS, SUPPLY AIR REGISTERS, SUPPLY AIR DISTRIBUTORS, EXHAUST REGISTERS, INTERIOR EXHAUST FANS, WALL FANS, GENERAL PURPOSE FANS, AXIAL FLOW FANS, CENTRIFUGAL FANS, WORKSHOP FANS, VENTILATION DUCTING AND DUCT SILENCERS, DUST HUMIDIFIERS, HEAT RECOVERY UNITS, HEAT PUMPS, SOLAR COLLECTORS, BARK DRYERS