| Business | Phone |
| Abe Environmental Systems 806 E 4th St, Duluth 55805 | (218) 727-1767 |
| J & W Instruments 202 N Hawthorne Rd, Duluth 55812 | (218) 728-2373 |
| Johnson Controls Inc 4627 Airpark Blvd, Duluth 55811 | (218) 727-8996 |
| Siemens Building Technologies 11 E Superior St, Duluth 55802 | (218) 625-2230 |
| Temperature Control Svc 2000 W Superior St, Duluth 55806 | (218) 624-4629 |