| CLASS | TRADE |
|---|---|
| C36 | PLUMBING CONTRACTOR |
| C16 | FIRE PROTECTION CONTRACTOR |
| C34 | PIPELINE CONTRACTOR |
| C42 | SANITATION SYSTEM CONTRACTOR |
| C-4 | BOILER, HOT WATER HEATING AND STEAM FITTING CONTRACTOR |
| C20 | WARM-AIR HEATING, VENTILATING AND AIR-CONDITIONING CONTRACTOR |
| A | GENERAL ENGINEERING CONTRACTOR |
| C38 | REFRIGERATION CONTRACTOR |
| HAZ | HAZARDOUS SUBSTANCE REMOVAL CERTIFICATION |