See UL Listed. See also CE and ETL. While Underwriters Laboratories would like everyone to think only THEY can make something "Listed," they are not the only players in the game. Even though theirs is the only approval recognized by the NFPA. However, whatever NRTL (Nationally Recognized Testing Laboratory) you use (ETL, UL, or others), they will still test an electrical product to the UL standard that applies to that particular equipment. NRTL's other than UL do not write standards. Market acceptance of UL as an assurance of safety is almost universal. The same cannot be said of other NRTL's.