This unit group includes heating, refrigeration, air conditioning, millwrighting and elevator and other equipment installation and mechanic trades contractors who own and operate their own businesses. This group also includes supervisors who supervise and co-ordinate the activities of workers classified in unit groups within the following minor groups: Machinery and Transportation Equipment Mechanics (Except Motor Vehicle) (731), Automotive Service Technicians (732) and Other Mechanics (733). They are employed in a wide range of establishments; places of employment are indicated in the unit group descriptions of the above minor groups.