Which UL Standard must qualified electrical testing laboratories utilize for evaluating snap switches?

The correct standard for evaluating snap switches is UL 20. This standard specifically addresses the safety and performance requirements for snap switches used in various applications, including those found in residential and industrial settings.

UL 20 establishes criteria for construction, performance, and testing that ensure the safety and reliability of snap switches. This is particularly important in maintaining safe electrical systems, as these devices control the flow of electricity and are integral to preventing electrical hazards.

The other standards mentioned focus on different types of equipment or materials. For example, UL 499 pertains to heating appliances, UL 94 deals with flammability testing of plastic materials, and UL 67 covers panelboards and associated equipment. These standards are important in their respective areas, but they do not apply to snap switches.