High quality safes should come with a fire resistance rating to signify that the safe has been extensively tested to resist high temperature from fires and protect the contents of the safe from destruction. There are a couple different testing sources for safe fire ratings, each performing and measuring their fire test slightly differently. All fire tests, however, aim to achieve an internal safe temperature resistance of less than 350 degrees Fahrenheit since any temperatures above this will incinerate paper. In addition to this minimum temperature standard, fire ratings are based on classifications related to type, length, and severity of the test. Here is a closer look at fire testing and ratings.

Into the Fire

There are a number of different fire testing standards, including: Korean Industrial Standards, Underwriters’ Laboratories, and Private Label Testing. Each of these standards adheres to similarly strict protocols for evaluating safes for fire resistance, but Underwriters’ Laboratories is considered to be one of the most comprehensive. Private Label testing is when a manufacturer hires an independent testing laboratory to perform the fire testing. For every testing procedure, there are three primary tests that are performed to achieve the classification for fire resistance: fire endurance test, explosion hazard test, and fire impact test.

Measuring Resistance

Different classifications of fire resistance pertain to different exposure times and temperatures of safes to fires. Underwriters’ Laboratories maintain 5 classes for safes–letters A-E. Safes in classes A, B, and C are subjected to each of these three tests, while safes in classes D and E are only tested for fire endurance and explosion hazard.

  • Fire Endurance Test- This is the most basic and universal of fire resistance testing on safes. This test involves measuring the resistance of the safe to a range of temperatures based on standardized fire exposure conditions. The safe is first placed in a cold furnace with all exterior surfaces exposed and papers scattered around the interior.A measuring device is placed inside, the safe is sealed and the fire is started in the furnace. The heat in the furnace is then gradually increased to the specified temperatures and the fire is equally distributed across the entire safe. The safe remains in the furnace for specified classification time until the fire is extinguished and the safe allowed to cool. Class A receives the longest time in the furnace at the highest temperature–4 hours reaching 2000 F. Other classes are exposed for slightly less time at lower temperatures.Once the safe has cooled, it is opened and the contents are examined. To pass, the records must be usable and the interior must not show excessive signs of heat transmission. In short, the interior of the safe must not record temperatures exceeding 350 F.


  • Explosion Hazard Test- This test is meant to measure whether the safe can protect against explosions from sudden, intense heat exposure. In faulty safes, sudden high temperatures can cause the hydrogen-air stream mixtures inside the safe to explode, rupturing the safe’s insulation and walls, compromising the fire resistance of the safe.The test involves heating the furnace to 2000 degrees, inserting the safe, closing the furnace for 30 minutes to observe the safe in a constant 2000 degree fire. Once the safe is removed from the furnace and has cooled, it is examined for ruptures. If none is found, the safe passes.


  • Fire Impact Test- This test measures the resistance of the safe under extreme heat then subjects the safe to a drop test down three building floors. The safe is heated and hoisted 30 feet above a concrete floor. It is then dropped and allowed to lie in burning embers until eventually cooled. Once this is complete, the safe is inverted and re-installed in the furnace for another temperature resistance test. The records inside the safe must be usable when the safe is opened in order to pass.

These fire resistance tests make quality safes the fortified investments they are renowned for being. An Underwriters’ Laboratories fire rating is the most respected testing and fire ratings in the world due to these high standards, so a safe with a UL fire rating is likely to be a quality, highly resistance piece of equipment.