Installs, repairs, inspects, maintains, tests, modifies, etc. a variety of heating, ventilating, air conditioning (HVAC), commercial natural gas, compressed air, control and oil systems and related components and equipment. Installs, repairs, inspects, maintains, tests, modifies, etc. a variety of piping systems related components and equipment including but not limited to: refrigerant, steam, condensate, vacuum, water, commercial natural gas, compressed air, control air, etc.