| Aspect | D155 | D156 |
|---|
| Required Certifications | HVAC Certification, EPA 608 | HVAC Certification, EPA 608 |
| Work Environment | Commercial and residential HVAC systems | Commercial and residential HVAC systems |
| Industry Usage | Heating, Ventilation, Air Conditioning | Heating, Ventilation, Air Conditioning |
Both D155 and D156 roles typically require similar certifications and work in comparable environments within the HVAC industry. The main difference lies in specific job duties or employer preferences, but generally, they are closely related positions focused on HVAC system installation and maintenance.