| Airhandler's Mechanical Services, Inc. | Magnolia | NJ | $0 |
| Air Management Systems, Inc. | Baxley | GA | Subcontractor |
| Air Management Technologies, Inc. | Lewisburg | PA | $0 |
| Airmaster Heating & Cooling, Inc. | Easton | MD | $0 |
| Air-o Heat & Air Conditioning, Inc. | Stillwater | OK | Subcontractor |
| Air Quest America, Inc. | Maynardville | TN | $0 |
| Airrow Heating & Sheet Metal LLC | Newport | OR | $0 |
| Air Source Alaska, LLC | Anchorage | AK | Subcontractor |
| Air Stream General Construction , Inc. | San Antonio | TX | $0 |
| Air System Designs LLC | Barceloneta | PR | $0 |
| Air Systems Balancing And Testing Service, Inc. | Rush | NY | $0 |
| Air Systems Engineering, Inc. | Tacoma | WA | Subcontractor |
| Air Systems, Inc. | San Jose | CA | $0 |
| Airtech Mechanical Corporation | Commerce City | CO | $0 |
| Air Temp Heating LLC | Price | UT | $0 |
| Airtest Co. LLC | Mountlake Terrace | WA | Subcontractor |
| A. J. Allen Mechanical Contractors, Inc. | Des Moines | IA | Subcontractor |
| Akia Services Co. | Tahlequah | OK | $0 |
| A Kool Saver Inc. | Miami | FL | $0 |
| Albany Air Conditioning And Heating Co. Inc. | Albany | GA | $0 |
| Albdr For Air Condition Ltd. | Jerusalem | | $0 |
| Albert Arno, Incorporated | Saint Louis | MO | Subcontractor |
| Alj Heating & Cooling LLC | Latham | NY | $0 |
| Al Kulaib International Trading Company WLL | Kuwait City | | $0 |
| All City Mechanical Inc. | North Little Rock | AR | Subcontractor |
| Allen Kelly & Co. Inc. | Raleigh | NC | $0 |
| Alliance Fire Protection Inc. | Albuquerque | NM | Subcontractor |
| Alliance Fire Protection Services, Inc. | Loganville | GA | $0 |
| Alliant Systems LLC | Portland | OR | $0 |
| Allied Mechanical, Inc. | Orange | TX | $0 |
| Allied Piping Company | Johnson City | TN | $0 |
| Allison Mechanical Inc. | Redlands | CA | $0 |
| Allred Mechanical Services Inc. | Rocky Mount | NC | $0 |
| Allstates Mechanical Ltd. | Garnet Valley | PA | $0 |
| Alpha Air Balancing Agency, Inc. | Carmel | CA | $0 |
| Alpha Plumbing Ltd. | Pasadena | MD | $0 |
| Alpine Heating & Air Conditioning Inc. | Idaho Falls | ID | $0 |
| Althoff Industries, Inc. | Crystal Lake | IL | $0 |
| Amber Mechanical Contractors Inc. | Alsip | IL | $0 |
| Ambient Air Control Systems | Alpine | CA | Subcontractor |
| A M D Mechanical Services LLC | Hughesville | MD | $0 |
| A.m.e. Inc. | Fairfield | NJ | $0 |
| American Air Balance Co. Inc. | Anaheim | CA | Subcontractor |
| American Air Solutions LLC | Sierra Vista | AZ | Subcontractor |
| American Hvac, Inc. | Pompano Beach | FL | $0 |
| American Mechanical Contractors, Inc. | Kingsport | TN | Subcontractor |
| American Mechanical Group Inc. | Columbus | OH | $0 |
| American Mechanical Inc. | Kechi | KS | Subcontractor |
| American Mechanical, Inc. | Walnut Creek | CA | Subcontractor |
| American Mechanical Services Of Houston, L.L.C | Stafford | TX | $0 |
| A & M Heating & Cooling, Inc. | Saint Joseph | MO | $0 |
| Ami Mechanical Corp. | Albuquerque | NM | Subcontractor |
| Anania Plumbing And Heating, Inc. | Brockton | MA | $0 |
| Anchor Mechanical, Inc. | Chicago | IL | $0 |
| Anderson Piping Company, Inc. | Nashville | TN | $0 |
| Anderson Rowe & Buckley Inc. | San Francisco | CA | $0 |
| Anhar Missan Company For General Trading LLC | Baghdad | | Subcontractor |
| Anthony Mechanical, Inc. | Lubbock | TX | $0 |
| Apex Fire Protection, Inc. | Montrose | CA | Subcontractor |
| Apex Mechanical Systems Inc. | Englewood | OH | Subcontractor |
| Apex Refrigeration & Boiler Co. | Phoenix | AZ | $0 |
| Api Group Life Safety USA LLC | Kansas City | KS | Subcontractor |
| Apperson Plumbing Inc. | Newburg | MD | $0 |
| Archer Mechanical & Maintenance Contractors Inc. | Salt Lake City | UT | Subcontractor |
| Arctic Chill & Heating Solutions LLC | Anchorage | AK | Subcontractor |
| Arctic Cooling & Heating, Inc. | Grand Junction | CO | $0 |
| Arctic Innovation Systems LLC | Silver Spring | MD | $0 |
| Arctic Refrigeration, Inc. | Ellicott City | MD | $0 |
| Arena Fire Protection, Inc. | Mobile | AL | Subcontractor |
| Aries Fire Protection Inc. | Hackensack | NJ | Subcontractor |
| Aries Mechanical, Inc. | Lakewood | WA | Subcontractor |
| Ariosa & Company, LLC | Cockeysville | MD | Subcontractor |
| Arizona Style Construction, LLC | Tucson | AZ | $0 |
| Arizona Valley Refrigeration Heating & Cooling, LLC | Yuma | AZ | $0 |
| Arnold's Refrigeration, Inc. | Cheboygan | MI | $0 |
| Art Newsome Inc. | Newport News | VA | $0 |
| Asher Contractors LLC | San Antonio | TX | $0 |
| Asp Mechanical, Inc. | Hermantown | MN | $0 |
| Associated Fire Protection Corp. | East Syracuse | NY | Subcontractor |
| Associated Mechanical Companies Inc. | Chesapeake | VA | Subcontractor |
| Associate Mechanical Contractors Inc. | Escondido | CA | Subcontractor |
| A & S Sprinkler Company, Inc. | Cheltenham | PA | Subcontractor |
| A Team Enterprises LLC | Sykesville | MD | $0 |
| A & T Heating And Air Conditioning Corp. | Bountiful | UT | $0 |
| Athena Engineering, Inc. | San Dimas | CA | Subcontractor |
| Atlantech Mechanical Services, LLC | Chesapeake | VA | $0 |
| Atlantic Cooling Technologies And Services, LLC | Carlstadt | NJ | Subcontractor |
| Atlas Mechanical, Inc. | San Diego | CA | Subcontractor |
| August Winter & Sons, Inc. | Appleton | WI | Subcontractor |
| Aures And Galey Hvac Service Corporation | West Berlin | NJ | $0 |
| Automated Solutions Group, Inc. | San Jose | CA | Subcontractor |
| Automatic Fire Protection LLC | Pearl River | LA | Subcontractor |
| Automatic Fire Protection, LLC | Richardson | TX | Subcontractor |
| Automatic Fire Sprinkler LLC | Normal | IL | $0 |
| Aven Fire Systems Inc. | New Castle | PA | $0 |
| Awl Industries Inc. | Brooklyn | NY | $0 |
| A&w Plumbing & Heating, Inc. | Murphysboro | IL | $0 |
| Axis Control Solutions LLC | Lewisburg | PA | Subcontractor |
| Az Fire Sprinklers LLC | Camp Verde | AZ | $0 |
| Backflow Technology, LLC | Ashburn | VA | $0 |
