| 230000 | Heating, Ventilating and Air Cond. (HVAC) |
| 230100 | Operation and Maintenance of HVAC Systems |
| 230120 | Operation & Main.-HVAC Piping & Pumps |
| 230130 | Operation and Maintenance-HVAC Air Distribution |
| 230500 | Common Work Results for HVAC |
| 230593 | Testing, Adjusting and Balancing for HVAC |
| 230670.16 | Packaged Outdoor HVAC Equipment Sch |
| 230700 | HVAC Insulation |
| 230713 | Duct Insulation |
| 230716 | HVAC Equipment Insulation |
| 230719 | HVAC Piping Insulation |
| 230933 | Electric & Electronic Control System for HVAC |
| 232000 | HVAC Piping and Pumps |
| 232100 | Hydronic Piping and Pumps |
| 232113 | Hydronic Piping |
| 232123 | Hydronic Pumps |
| 232200 | Steam and Condensate Piping and Pumps |
| 232300 | Refrigerant Piping |
| 233* | Building, Developing and General Contracting |
| 233000 | HVAC Air Distribution |
| 233113.13 | Rectangular Metal Ducts |
| 2332* | Residential Building Construction |
| 23331* | Manufacturing and Light Industrial Building Construction |
| 23332* | Commercial and Institutional Building Construction |
| 233813 | Commercial-Kitchen Hoods |
| 2341* | Highway, Street, Bridge and Tunnel Construction |
| 23411* | Highway and Street Construction |
| 23412* | Bridge and Tunnel Construction |
| 23491* | Water, Sewer and Pipeline Construction |
| 23499* | All Other Heavy Construction |
| 235000 | Central Heating Equipment |
| 2351* | Plumbing, Heating and Air Conditioning Contractors |
| 2352* | Painting and Wall Covering Contractors |
| 235200 | Heating Boilers |
| 2353* | Electrical Contractors |
| 2354* | Masonry and Stone Contractors |
| 235400 | Furnaces |
| 23542* | Drywall, Plastering, Acoustical and Insulation Contractors |
| 23543* | Tile, Marble, Terrazzo and Mosaic Contractors |
| 23551* | Carpentry Contractors |
| 23552* | Floorlaying and Other Floor Contractors |
| 23561* | Roofing, Siding and Sheet Metal Contractors |
| 2357* | Concrete Contractors |
| 23591* | Structural Steel Erection Contractors |
| 23593* | Excavation Contractors |
| 23594* | Wrecking and Demolition Contractors |
| 23599* | All Other Special Trade Contractors |
| 236115* | New Single-Family Housing Construction (except Operative Builders) |
| 236116 | Reciprocating Refrigerant Compressors |
| 236116* | New Multifamily Housing Construction |
| 236118 | Residential Remodelers |
| 2362* | Nonresidential Building Construction |
| 2362* | Nonresidential Building |
| 236200 | Packaged Compressor and Condenser Units |
| 236210* | Industrial Building Construction |
| 236220* | Commercial and Institutional Building Constr |
| 237* | Heavy and Civil Engineering Construction |
| 237000 | Central HVAC Equipment |
| 237110* | Water and Sewer Line and Related Structures Construction |
| 237120* | Oil and Gas Pipeline and Related Structures Const. |
| 237130* | Power and Communication Line and Related Structures Construction |
| 237210* | Land Subdivision |
| 237310* | Highway, Street, and Bridge Construction |
| 237990* | Other Heavy & Civil Engineering Construction |
| 2381* | Foundation, Structure, and Building Exterior Contractors |
| 238110* | Poured Concrete Foundation and Structure Contractors |
| 238119 | Self-Contained Air-Conditioners |
| 238120* | Structural Steel and Precast Concrete Contractors |
| 238130* | Framing Contractors |
| 238140* | Masonry Contractor |
| 238160 | Roofing Contractors |
| 238160* | Asphalt Roof Shingle Installation |
| 238170* | Siding Contractors |
| 238190* | Other Foundation, Structure, and Building Exterior Contractors |
| 238210* | Electrical Contractors and other Wiring Installation Contractors |
| 238220 | Pumping system, water, installation |
| 238220* | Plumbing, Heating, and Air-Conditioning Contractors |
| 238290* | Other Building Equipment Contractors |
| 238310* | Drywall and Insulation Contractors |
| 238320* | Painting and Wall Covering Contractors |
| 238330* | Flooring Contractors |
| 238340 | Tile and Terrazzo Contractors |
| 238350* | Finish Carpentry Contractors |
| 238390* | Other Building Finishing Contractors |
| 2389* | Other Specialty Trade Contractors |
| 238910* | Site Preparation Contractors |
| 238990* | All Other Specialty Trade Contractors |