All standard overcurrent protective devices (OCPD) mounted in enclosures(i.e. breakers in panels or fuses in safety switches) are tested to protect conductors which have been sized at 125% of their continuous loading. Enclosed OCPDs intended for 100% loading require "special" ventilated enclosures. Open air testing/rating of OCPD are usually not applicable in the real world.
The application of OCDPs mimic the rating and application of conductors in regards to raceways versus open air as well as different ambient temperatures.
