Nationally Recognized Testing Laboratory, one example of which is Underwriters Laboratories, Inc. (UL).
National Recognized Test Laboratory - a laboratory accredited by OSHA, the US Occupational Safety and Health Administration.
Acronym for "Nationally Recognized Testing Laboratory."
Technically, the term NRTL Nationally Recognized Testing Lab is only applicable to third-party testing organizations recognized by OSHA. Therefore, technically the term only applies to safety requirements in the US.