37 Installation, maintenance and repair of hardware for data communication networks; installation of heating, refrigerating, air conditioning, drying, ventilating and dust extraction apparatus; repair and maintenance of heating, refrigerating, air conditioning, drying, ventilating and dust extraction apparatus; retrofitting of ventilating installations in buildings: retrofitting of heating, ventilating and air conditioning installations in buildings; construction services relating to the installation of heating, ventilating and air conditioning systems; installation, maintenance and repair of automatic apparatus for opening and closing ventilation flaps; installation of air conditioning apparatus: repair and maintenance of air conditioning apparatus; repair or maintenance of air conditioning apparatus; installation, maintenance and repair of apparatus for heating, purifying air, refrigerating, drying, ventilating, temperature control and air conditioning; installation and repair of air conditioning systems: installation of environmental protection systems; installation of environmental control systems: installation, maintenance and repair of cooling and air conditioning systems for temperature-controlled environments; installation of air conditioning apparatus for use in clean rooms; installation, construction, maintenance, servicing and repair of energy and power generating apparatus, equipment and installations: construction of energy efficient buildings and structures