| Employer | State | City | |
| C.R.S. Inc | Massachusetts | N. Billerica | View Profile |
| C.R.S. Inc | Massachusetts | N. Billerica | View Profile |
| Cam-Ful Industries | North Carolina | Pineville | View Profile |
| Cam-Ful Industries | North Carolina | Pineville | View Profile |
| Capitol Boiler Works Inc | Virginia | Springfield | View Profile |
| Carrano Aircontracting, Inc. | New Jersey | Dayton | View Profile |
| Carrier Great Lakes | Michigan | Livonia | View Profile |
| Carter Goble Lee Company | Georgia | Alpharetta | View Profile |
| Cary Services Inc | Texas | Abilene | View Profile |
| CCI Mechanical, Inc. | Utah | Salt Lake City | View Profile |
| Central Carolina Air Conditioning | North Carolina | Greensboro | View Profile |
| Central Carolina Air Conditioning | North Carolina | Greensboro | View Profile |
| CHC Mechanical Contractors | Tennessee | Cookeville | View Profile |
| Christian Brothers Mechanical Services, Inc. | California | Mira Loma | View Profile |
| City Wide Mechanical | Texas | Dallas | View Profile |
| City Wide Mechanical | Texas | Dallas | View Profile |
| Classic Air | Georgia | Norcross | View Profile |
| Climate Control Company of Glenwood Springs | Colorado | Glenwood Springs | View Profile |
| Climate Heating & Cooling | Massachusetts | Dalton | View Profile |
| Climate Technology | Colorado | Colorado Springs | View Profile |
| ClimateCraft | Oklahoma | Oklahoma City | View Profile |
| CLIMATIC REFRIGERATION & AC | Florida | Melbourne | View Profile |
| Clover Contracting, Inc. | Virginia | Fairfax | View Profile |
| CMS Mechanical Services, Inc. | Colorado | Windsor | View Profile |
| ColonialWebb Contractors | Virginia | Richmond | View Profile |
| Comfortrol | Ohio | Columbus | View Profile |
| Commercial Comfort Service, Inc. | Massachusetts | Tewksbury | View Profile |
| Commercial Environmental Solutions | Maryland | Fulton | View Profile |
| Commercial Kitchen Repair | Texas | San Antonio | View Profile |
| Commercial Kitchen Repair | Texas | San Antonio | View Profile |
| Commercial Mechanical Systems, Inc. | North Carolina | Raleigh | View Profile |
| Commercial Mechanical Systems, Inc. | North Carolina | Raleigh | View Profile |
| Complete Building Services | District of Columbia | Washington | View Profile |
| Comprehensive Energy Services, Inc. | Florida | Longwood | View Profile |
| Comverge, Inc. | Georgia | Norcorss | View Profile |
| Control and Equipment Co. | Texas | El Paso | View Profile |
| Controlled Combustion Co. Inc. | New York | Bronx | View Profile |
| Controlled Environment Technologies | Pennsylvania | York | View Profile |
| Cool-Rite, LLC | Florida | Orlando | View Profile |
| Cooper Electric Supply Co | New Jersey | Tinton Falls | View Profile |
| Cottongim Heating & Cooliing, Inc. | Georgia | Tifton | View Profile |
| Cottongim Heating & Cooliing, Inc. | Georgia | Tifton | View Profile |
| County Air | California | Orange | View Profile |
| Crockett Facilities Services, Inc. | Maryland | Bowie | View Profile |
| Crowther Roofing & Sheet Metal | Illinois | Lockport | View Profile |
| CTC Supply Inc. | North Carolina | Fayetteville | View Profile |
| CTS Services | Maryland | Beltsville | View Profile |
| Cunningham Inc | Iowa | Oskaloosa | View Profile |
| Curtis Total Service, Inc. | Pennsylvania | Allentown | View Profile |