37 Installation, maintenance, and repair of pipes, valves, meters, trucks, tanks and storage vessels used in the supply of natural and liquefied petroleum gas to residential, commercial and industrial users; installing, maintenance, and repair of gas fired appliances and equipment, namely, air conditioners, boilers, burners, carbon dioxide generators, clothes dryers, coffee makers, deep fat fryers, dish washers, food and dish warmers, furnaces, fireplaces, fireplace heaters, space heaters, water heaters, swimming pool heaters, hot plates and griddles, humidifiers, incinerators, ovens, ranges, smoke houses, toasters, barbecues and lights; installing, maintenance, and repair of accessories for gas fired appliances and equipment, namely, automatic burner ignition and safety shut-off devices, combination controls for gas appliances, connectors for gas appliances, drip tubes for water heaters, draft hoods, petroleum gas hose, couplings and assemblies, pressure regulators, quick-disconnect devices, thermostats, and valves; installing, maintenance, and repair of household appliances, namely, electric dishwashers, electric clothes washers, electric refrigerators, electric freezers, electric dryers, barbeques, barbeque accessories, trashmashers, microwave ovens, air cleaners, dehumidifiers, vacuum cleaners, central vacuum cleaners, humidifiers, dehumidifiers, smoke and fire detectors, household security systems and fire extinguishers; installing insulation, aluminum doors and windows; installing external and internal air filtration controls for buildings and providing energy management, measurement and consulting services; repair, maintenance, and installation of natural gas vehicle equipment and accessories; pipeline maintenance services; construction and installation of pipelines; water well and oil drilling; conservation in the nature of home energy assessment services for the purpose of determining home improvements needed to improve energy use and efficiency relating to petroleum, refined petroleum products, natural and liquefied gas, electrical energy, oil, propane and water on behalf of others; consulting services in the field of pipeline maintenance