To earn the UL Classification, sample files are subjected to the following tests:

Explosion Hazard Test: A file is placed in a preheated 2,000 degree furnace for 30 minutes to ensure gasses do not build up inside that may result in an explosion.

Fire Endurance Test: A file is placed in a 1,700 degree furnace for a one hour period while the interior temperature is monitored via thermocouples, ensuring that interior temperatures do not exceed 350 degrees.

Fire & Impact Test: (Only performed on files that carry the "Fire & Impact" rating). A file is placed in a furnace preheated to 1,550 degrees for 30 minutes. The file is then removed from the oven, raised 30 feet and dropped over a bed of rocks and rubble to simulate the effect of collapsing floors and ceilings. The file is then inverted and reheated to 1,550 degrees for an additional half hour. Only after this abuse and constant monitoring of the file's interior drawer temperature to ensure it never reaches the 350 degree threshhold, has a file successfully completed this test.

To learn more about Underwriters Laboratories and the UL mark that appears on our insulated products, feel free to visit their web site.