| Air Tight | Jackie Lou Mc Beth | — | (707) 822 8800 | HVAC | Arcata · Humboldt County | — | — |
| Bell's Heating | Bell's Heating | — | (707) 442 7616 | HVAC | Eureka · Humboldt County | — | — |
| Besc INC DBA California Heating | Timothy James Twomey | — | (707) 826 9008 | HVAC | Arcata · Humboldt County | — | — |
| Bob's Heating And Air Solutions INC | Robert Eugene Iii Secor | — | (707) 798 1997 | HVAC | Eureka · Humboldt County | — | — |
| D C Mechanical | D C Mechanical | — | (707) 599 5439 | HVAC | Cutten · Humboldt County | — | — |
| Evans Mechanical INC | Joseph Scott Tanno Senior | — | (707) 445 1435 | HVAC | Eureka · Humboldt County | — | — |
| Excel Heating And Cooling LLC | Stephen Spencer Carmichael | — | (707) 346 4264 | HVAC | Mc Kinleyville · Humboldt County | — | — |
| Foi | Robert Charles Mc Beth | — | (707) 822 8800 | HVAC | Arcata · Humboldt County | — | — |
| Greenwired INC | Joshua Lane Miller | — | (707) 923 2001 | HVAC | Redway · Humboldt County | — | — |
| Humboldt Mechanical Solutions | Humboldt Mechanical Solutions | — | (707) 616 7420 | HVAC | Arcata · Humboldt County | — | — |
| James L Parra | James L Parra | — | (714) 853 3273 | HVAC | Blue Lake · Humboldt County | — | — |
| Jaymes Refrigeration Service | Jayme Javier Gonzales | — | (707) 382 6978 | HVAC | Fortuna · Humboldt County | — | — |
| Mac's Refrigeration Service | David Lee Mc Donald | — | (707) 442 8712 | HVAC | Eureka · Humboldt County | — | — |
| Mapleservice Incorporated | Roger Lee Maples | — | (707) 445 9671 | HVAC | Eureka · Humboldt County | — | — |
| Niekrasz Plumbing INC | Gregory Albert Niekrasz | — | (707) 442 7181 | HVAC | Eureka · Humboldt County | — | — |
| Nor Cal Mechanical LLC | Janice Mary Masterson | shawn@norcalmechanical.com | (707) 223 2100 | HVAC | Garberville · Humboldt County | — | — |
| O & M Industries | Kenneth George Christen | info@omindustries.com | (707) 822 8800 | HVAC | Arcata · Humboldt County | — | — |
| Precision Heating And Air Conditioning LLC | Ben Jacobsen | — | (707) 683 6452 | HVAC | Fortuna · Humboldt County | — | — |
| Redwood Mechanical | Redwood Mechanical | — | (707) 273 5066 | HVAC | Eureka · Humboldt County | — | — |
| Scurfield Electric Heating & Solar | Benjamin Garland Scurfield | — | (707) 825 0759 | HVAC | Arcata · Humboldt County | — | — |
| Six Rivers Mechanical INC | Jeffrey Allen Schafer | — | (707) 499 5867 | HVAC | Eureka · Humboldt County | — | — |
| Spaulding Mechanical | Spaulding Mechanical | — | (707) 498 9425 | HVAC | Eureka · Humboldt County | — | — |
| Wayne Maples Plumbing & Heating INC | Shawn Brendon Maples | — | (707) 445 2500 | HVAC | Eureka · Humboldt County | — | — |
| Whitson INC | Richard David Reinhard | — | (707) 845 8107 | HVAC | Willow Creek · Humboldt County | — | — |