installation and repair of heating; installation, maintenance and repair of ventilating systems; maintenance and repair of air conditioners; installation, maintenance and repair of apparatus for heating, purifying air, refrigerating, drying, ventilating, temperature control and air-conditioning; installation, maintenance and repair of heating systems; installation, maintenance and repair of heating, ventilation and air-conditioning [HVAC] systems; maintenance and repair of heating systems; maintenance and repair of heating installations; installation, maintenance and repair of HVAC [heating, ventilation and air conditioning] systems; installation of heating, ventilation and air-conditioning [HVAC] systems; heating installation and repair; heating system installation, repair and maintenance; heater installation, repair and maintenance services; installation, maintenance and repair of air-conditioning apparatus; installation of central heating systems; installation and repair of heating, ventilating and air-conditioning systems; installation of central heating; heating system installation, repair and maintenance services; installation, maintenance and repair of gas and electricity systems; installation, repair and maintenance of heating systems; routine servicing of heating, refrigerating, air-conditioning, drying, ventilating and dust extraction apparatus; heating equipment installation, repair and maintenance services; installation and repair of heating equipment; installation and maintenance of heating systems; repair and maintenance of air conditioners; installation, repair and maintenance services of heating equipment; central heating installation; installation and repair of heating systems; maintenance and repair of heating, refrigerating, air-conditioning, drying, ventilating and dust extraction apparatus; heating equipment installation, repair and maintenance; installation services of central heating; heating system maintenance and repair; maintenance and repair of heating equipment; installation of heating, ventilation and air-conditioning systems; repair or maintenance of gas water heaters; installation, maintenance and repair of air-conditioning systems; installation, repair and maintenance of heating equipment