This group includes heating, refrigeration, air conditioning, millwrighting and elevator installation trade contractors who own and operate their own businesses.

This group also includes supervisors who supervise and co-ordinate the activities of workers classified in groups within the following areas: Machinery and Transportation Equipment Mechanics (Except Motor Vehicle), Automotive Service Technicians and Other Mechanics.

They are employed in a wide range of establishments; places of employment are indicated in the group descriptions.