Glossary
NRTL
A Nationally Recognized Testing Laboratory (NRTL) is a private lab, such as UL, recognised by the US Occupational Safety and Health Administration to test and certify product safety, most visibly for electrical equipment. NRTL listing is not the same as FCC certification.
Why it matters
NRTL listing is not a general legal requirement for retail consumer goods, but it is frequently demanded in practice by workplaces, retailers, insurers and local electrical inspectors, so many products end up needing it commercially even when no federal law forces the issue.