| L. Nothhaft & Son Inc. | Denver | CO | $0 |
| Lochridge-priest, Inc. | Waco | TX | Subcontractor |
| Locke Air Conditioning & Custom Sheet Metal, Inc. | El Centro | CA | $0 |
| Lockmer Plumbing Heating And Utilities Inc. | Butte | MT | $0 |
| Loescher Heating & Air Conditioning Co. | Freeport | IL | $0 |
| Lonoke Service Co. LLC | Lonoke | AR | $0 |
| Lor-mar Mechanical Services, LLC | Pennsauken | NJ | Subcontractor |
| Los Angeles Air Balance Co. Inc. | Upland | CA | Subcontractor |
| Los Angeles Air Conditioning Inc. | La Verne | CA | $0 |
| Losch Services Inc. | Schuylkill Haven | PA | Subcontractor |
| Louis N Picciano & Son Inc. | Binghamton | NY | Subcontractor |
| Lower Alabama Heating Cooling & Refrigeration, LLC | Chatom | AL | Subcontractor |
| LTJ Heating & Air Conditioning Inc. | Lancaster | CA | $0 |
| Lugaila Mechanical, Inc. | Pittsburgh | PA | Subcontractor |
| Lyons Company LLC | Glasgow | KY | $0 |
| Mackin & Little, Inc. | Spokane | WA | Subcontractor |
| Macs Heating Cooling & Electrical Inc. | Eddyville | KY | $0 |
| Maddox Air & Electrical, Inc. | Lynchburg | VA | $0 |
| Magothy Mechanical LLC | Severna Park | MD | Subcontractor |
| Maguire Company, Inc. | Newton | MA | $0 |
| Mallory Air Condition & Refrigeration | Thomaston | GA | $0 |
| Manhattan Welding Co. Inc. | Hillside | NJ | $0 |
| Manitowoc Heating & Refrigeration Services, Inc. | Manitowoc | WI | $0 |
| Mann Mechanical Co. Inc. | Decatur | GA | $0 |
| Marcel R Nadeau | Burlington | CT | $0 |
| Marquee Fire Protection, LLC. | Rocklin | CA | Subcontractor |
| Mar's Contractors, Inc. | Miami | FL | $0 |
| Marshall Mechanical, Inc. | Franklin | IN | Subcontractor |
| Martin Mechanical Inc. | Kansas City | MO | Subcontractor |
| Martin Petersen Company, Inc. | Kenosha | WI | Subcontractor |
| Maryland Mechanical Systems, Inc. | Baltimore | MD | Subcontractor |
| Mason Refrigeration, Inc. | Chandler | AZ | $0 |
| Master Mechanical Inc. | Saint Paul | MN | $0 |
| Master Mechanical Service Inc. | Papillion | NE | Subcontractor |
| Master Mechanical Services, Inc. | Opa Locka | FL | $0 |
| Master Mech. Corp. | Mcadoo | PA | $0 |
| Master Sheet Metal Inc. | Honolulu | HI | Subcontractor |
| Math Mechanical, LLC | Virginia Beach | VA | Subcontractor |
| Mazama Services, LLC | Albertville | AL | $0 |
| Mcarthur & Sons, Inc. | Lorain | OH | $0 |
| Mccarl's Services, Inc. | Cranberry Township | PA | $0 |
| Mccauley Mechanical Construction Inc. | Bridgeview | IL | Subcontractor |
| Mcclain Mechanical Systems, Inc. | Oceanside | CA | Subcontractor |
| Mccloskey Mechanical Contractors Inc. | Blackwood | NJ | Subcontractor |
| Mcclure Mechanical Systems Inc. | San Diego | CA | Subcontractor |
| Mccoy's Heating And Air, Inc. | Jackson | TN | $0 |
| Mcdowall Co. | Waite Park | MN | $0 |
| Mcfarlane, Inc. | Grand Forks | ND | $0 |
| MCG Mechanical Inc. | Anderson | SC | $0 |
| Mcgowan Water Conditioning, Inc. | Mankato | MN | $0 |
| Mcjasm, Inc. | Redding | CA | $0 |
| Mclain Plumbing & Electrical Service Inc. | Philadelphia | MS | $0 |
| Mcnair Family & Associates, LLC | Decatur | GA | $0 |
| Mcnamara Custom Services, Incorporated | Waco | TX | $0 |
| Mcphillips Plumbing, Heating & Air Conditioning Company | Cleveland | OH | $0 |
| Mcshane Mechanical Contracting Inc. | Commerce Township | MI | Subcontractor |
| Mcvicar General Services, LLC | Glen Rock | PA | Subcontractor |
| Mechanical Builders Inc. | Anchorage | AK | Subcontractor |
| Mechanical Concepts, L.L.C. | Shreveport | LA | Subcontractor |
| Mechanical Construction & Consulting, Inc. | Anchorage | AK | Subcontractor |
| Mechanical Construction & Services Inc. | Windham | NH | $0 |
| Mechanical Design Systems, Inc. | Clinton | MD | $0 |
| Mechanical Engineering And Construction LLC | Catonsville | MD | Subcontractor |
| Mechanical Masters, Inc. | Fort Collins | CO | $0 |
| Mechanical Service Corporation | Whippany | NJ | $0 |
| Mechanical Services Inc. | Marietta | GA | Subcontractor |
| Mechanical Solutions Construction Inc. | Englewood | CO | Subcontractor |
| Mechanical Specialists, Inc. | Wasilla | AK | Subcontractor |
| Mechanical Systems, Incorporated | Omaha | NE | $0 |
| Mechanical Systems Of Dayton Inc. | Dayton | OH | Subcontractor |
| Mechanical Systems & Services Inc. | Charlotte | NC | Subcontractor |
| Mechanical Technologies Inc. | Green Bay | WI | $0 |
| Mechanical Testing Services, LLC | Clifton Park | NY | Subcontractor |
| Mech One, Inc. | Escondido | CA | Subcontractor |
| Medina Group, LLC | San Juan | PR | Subcontractor |
| Medrep Technologies, Inc. | Punta Gorda | FL | $0 |
| Mercury Air Conditioning & Heating, Inc. | Lake Havasu City | AZ | $0 |
| Merit Mechanical Services, Inc. | Helena | MT | $0 |
| Mertz Enterprises, Inc. | Anaheim | CA | Subcontractor |
| Metro Air Conditioning Co. | Shawnee | KS | Subcontractor |
| Metro Mechanical Services LLC | Birmingham | AL | Subcontractor |
| Metropolitan Heat & Power Co. Inc. | Brooklyn | NY | $0 |
| MGM Associates Inc. | Guntersville | AL | $0 |
| Miami Water Heater, Inc. | Miami | FL | $0 |
| Michael D. Lay | Fresno | CA | $0 |
| Michigan Mechanical Ventures, LLC | Farmington Hills | MI | Subcontractor |
| Mick's Plumbing & Heating, Inc. | Thurmont | MD | Subcontractor |
| Mid-american Water & Plumbing Inc. | Manhattan | KS | Subcontractor |
| Middleton Inc. | Bryant | AR | Subcontractor |
| Mike Gowen Mechanical, Inc. | North Little Rock | AR | Subcontractor |
| Mike's Mechanical Services LLC | Lewiston | ID | Subcontractor |
| Miller Bonded, Inc. | Albuquerque | NM | Subcontractor |
| Miller Sheetmetal Inc. | Bremerton | WA | Subcontractor |
| Minot Plumbing & Heating Co. | Minot | ND | $0 |
| Minutemen Corporation | North Hampton | NH | $0 |
| Mission Mechanical Corp. | Indianapolis | IN | Subcontractor |
| Mitchell Plumbing & Heating Co. Inc. | Mitchell | SD | Subcontractor |
| Mixan Heating & Air Conditioning, Inc. | Omaha | NE | Subcontractor |
| M.j. Daly, LLC | Waterbury | CT | Subcontractor |
| M & J Enterprises International, Inc. | Winter Park | FL | Subcontractor |
