NRTL safety certification (UL, ETL)

OSHA's Nationally Recognized Testing Laboratory (NRTL) program recognizes laboratories qualified to test and certify products to US safety standards. A product listed by an NRTL (UL and ETL are familiar marks) has been tested to the applicable standard, such as UL 62368-1 for IT and audio/video equipment or an appliance-specific UL standard, and is subject to ongoing factory inspections.

Federal rules require NRTL-certified equipment in many workplace situations, and in practice certification is demanded far more widely: by retailers, by electrical inspectors enforcing codes, by insurers and by commercial buyers. Mains-powered products and power adapters are where it is most often required.

Where it bites: certification covers the exact construction tested, so changing a critical component (power supply, transformer, enclosure plastic, wiring) can require re-evaluation, and follow-up inspections add recurring fees.