What type of duct label usually indicates the system's classification?

The type of duct label that usually indicates the system's classification is UL 181. This designation refers to a standard set by Underwriters Laboratories for the construction and performance of ducts used in heating, ventilation, and air conditioning (HVAC) applications. A UL 181 label signifies that the duct complies with the rigorous testing criteria for safety and durability, which are essential aspects of system classification.

Ducts labeled with UL 181 are recognized for their effectiveness in preventing fires and managing airflow effectively. Therefore, the classification provided by this label assists in identifying the duct's suitability for various HVAC applications, ensuring that professionals can select the appropriate duct types for their projects based on established standards. Additionally, labels such as Class 0, HVAC Certified, or Type A may not specifically convey the comprehensive criteria relating to system classification as effectively as the UL 181 designation does.