| Cci Mechanical LLC | Anchorage | AK | $0 |
| C & C Plumbing & Heating LLP | Minot | ND | $0 |
| CCS Industrial Services, Inc. | Purvis | MS | Subcontractor |
| Cellular Site Services, LLC | Upper Marlboro | MD | $0 |
| Central Air & Heating Service, LLC | Harlingen | TX | $0 |
| Central Mechanical Construction Co. Inc. | Manhattan | KS | Subcontractor |
| Central Tech Services, Inc. | Sparks | MD | $0 |
| Century Fire Sprinklers, Inc. | Kansas City | MO | Subcontractor |
| Century Fire Systems, LLC | El Paso | TX | Subcontractor |
| Cerris Systems Iowa, Inc. | Des Moines | IA | Subcontractor |
| Cerris Systems Reno, Inc. | Reno | NV | Subcontractor |
| Cerris Systems West, Inc. | Las Vegas | NV | Subcontractor |
| Certified Air Balance Co. Inc. | Santa Fe Springs | CA | Subcontractor |
| CFP International LLC | Hagerstown | MD | Subcontractor |
| CFS Service Corp. | Woodbridge | VA | $0 |
| Champion Fire Protection Inc. | Savannah | GA | Subcontractor |
| Champion Industrial Contractors, Inc. | Modesto | CA | Subcontractor |
| Chapman Air Systems, Inc. | Oceanside | CA | Subcontractor |
| Charles Fabian Inc. | Cranford | NJ | $0 |
| Charles P Blouin Inc. | Seabrook | NH | Subcontractor |
| Charles T Romano | Alice | TX | Subcontractor |
| Charlie's Plumbing, Inc. | Houston | TX | $0 |
| Chase Plumbing And Mechanical, Inc. | Chattanooga | TN | $0 |
| Chattanooga Fire Protection, Inc. | Chattanooga | TN | $0 |
| CHC Mechanical Contractors Inc. | Cookeville | TN | $0 |
| Chesapeake Controls, Incorporated | Chesapeake | VA | $0 |
| Chesapeake Fire Protection, Inc. | Odenton | MD | Subcontractor |
| Chill-craft Company | Hanover | MD | $0 |
| Chiller Systems Inc. | Fargo | ND | $0 |
| Chinook Fire Protection LLC | Anchorage | AK | Subcontractor |
| Chuck's Plumbing And Heating, Inc. | Leavenworth | KS | $0 |
| Cimco Refrigeration Inc. | Mobile | AL | Subcontractor |
| Circulating Air, Inc. | North Hollywood | CA | Subcontractor |
| City Mechanical, Inc. | Hercules | CA | $0 |
| City Plumbing LLC | Philadelphia | PA | $0 |
| Clean Air Contractors Corp. | Vega Alta | PR | $0 |
| Clean Air Refrigerant Recovery & Reclaiming, Inc. | Norcross | GA | $0 |
| Cleanwater Corporation Of America | Marlette | MI | $0 |
| Clear Reflections, Inc. | Albuquerque | NM | Subcontractor |
| Climate Control, A Limited Liability Company | Cheyenne | WY | $0 |
| Climate Engineers, LLC | Hiawatha | IA | $0 |
| Climate Systems, Inc. | Sioux Falls | SD | Subcontractor |
| Clinton J Earl | Chico | CA | $0 |
| Coastal Heating And Cooling, LLC | Norfolk | VA | $0 |
| Coastal Mechanical Contractors Inc. | Houma | LA | $0 |
| Cobb Mechanical Contractors, Inc. | Colorado Springs | CO | Subcontractor |
| Coenen Mechanical, LLC | Appleton | WI | $0 |
| Coe Plumbing, Inc. | Oklahoma City | OK | $0 |
| Columbia Sheet Metal Company | North Windham | CT | Subcontractor |
| Comfortable Climate Heating & Air Conditioning Inc. | Hayes | VA | $0 |
| Comfort Climate Solutions LLC | Salt Lake City | UT | $0 |
| Comfort Dynamics, Inc. | San Leandro | CA | $0 |
| Comfort Engineering Company, Inc. | Tupelo | MS | $0 |
| Comfort Mechanical, Inc. | Santee | CA | Subcontractor |
| Comfort Solutions Of Tidewater, LLC | Virginia Beach | VA | Subcontractor |
| Comfort Systems USA Intermountain, Inc. | Salt Lake City | UT | Subcontractor |
| Comfort Systems USA Mid South Inc. | Montgomery | AL | Subcontractor |
| Comfort Systems USA (northwest), Inc. | Woodinville | WA | $0 |
| Comfort Systems USA Shoffner, Inc.Blountville, TN · UEI GQ6BHJF434C3 | Blountville | TN | Subcontractor |
| Comfort Systems USA Shoffner, Inc.Knoxville, TN · UEI V5FMH8U8N8P6 | Knoxville | TN | Subcontractor |
| Comfort Systems USA (syracuse), Inc. | East Syracuse | NY | $0 |
| Commercial Refrigeration Of Harrisburg Inc. | Harrisburg | PA | $0 |
| Commercial Sheetmetal Co. Inc. | Waipahu | HI | Subcontractor |
| Commonwealth Fire Protection Co. | Leola | PA | $0 |
| Complete Mechanical & Electrical Solutions LLC | Rockville | MD | Subcontractor |
| Comprehensive Energy Services, Inc. | Longwood | FL | $0 |
| Concord Mechanical Inc. | Boyd | TX | Subcontractor |
| Conley Sprinkler, Inc. | Pleasanton | KS | Subcontractor |
| Control Air Enterprises LLC | Anaheim | CA | $0 |
| Control Systems Services Inc. | Washingtonville | NY | $0 |
| Cool-breeze Air Conditioning Corporation | Miami | FL | $0 |
| Cooney Refrigeration LLC | Clay Center | NE | $0 |
| Cooper Oates Air Conditioning Inc. | Sacramento | CA | $0 |
| Corning Appliance Corporation | Corning | NY | $0 |
| Corporate Mechanical Inc. | Minneapolis | MN | $0 |
| Corrigan Brothers, Inc. | Saint Louis | MO | Subcontractor |
| Corvus Co. For Gen. Trading Ltd. | Erbil | | Subcontractor |
| Cosgrove's North End Plumbing | Scranton | PA | Subcontractor |
| County Burner & Machinery Corp. | San Diego | CA | $0 |
| County Plumbing & Heating, Inc. | Lutsen | MN | $0 |
| Couts Heating & Cooling, Inc. | Corona | CA | Subcontractor |
| Cox-powell Corporation | Williamsburg | VA | Subcontractor |
| Craddock Mechanical, LLC | Oakland | MD | $0 |
| Craigs Air Conditioning Inc. | Kapolei | HI | $0 |
| Crecelius, Inc. | Blythe | CA | $0 |
| Crespo Refrigeration Service & Air Conditioning, LLC | Mayaguez | PR | $0 |
| Critchfield Mechanical Inc. | San Jose | CA | Subcontractor |
| Cross - K Enterprises Inc. | Newberry | MI | $0 |
| Cross Plumbing, Inc. | Villa Rica | GA | $0 |
| CSM Mechanical, LLC | Milford | MI | $0 |
| Ct Mechanical LLC | Addison | IL | $0 |
| Cullum Constructors, Inc. | North Charleston | SC | Subcontractor |
| Cullum Mechanical, LLC | North Charleston | SC | Subcontractor |
| Custom Mechanical Systems, Inc. | Wasilla | AK | $0 |
| C. V. Carlson Company, Inc. | White Plains | MD | Subcontractor |
| C. W. Suter & Son, Inc. | Sioux City | IA | $0 |
| D'agostino Mechanical Contractors, Inc. | Kansas City | KS | $0 |
| Damon-marcus Co. | Bartlett | TN | $0 |
| Damon Refrigeration Co. Inc. | Auburn | ME | $0 |
| Danny S Roggeman | Portland | TX | $0 |
