And, most important, UL is not so much concerned with electrical shock hazard (that is more of a OSHA or Consumer Product Safety Issue (in the US)), but with whether the device can start a fire. UL is Underwriter's Labs .. those are fire insurance underwriters being referred to. In some cities and counties (e.g. Los Angeles) it is illegal to sell any device not UL listed, or alternately, certified by a Los Angeles mfr approved to do this.