The vast majority of fire or fire/burglary safes, are built with an outer steel shell and an inner steel shell. The space between the steel layers is filled with a poured-in composite material similar to concrete. (Note that box stores sell frequently sell safes with plastic inner linings, and even plastic on the outside — don’t waste your money.) Photo on left shows a high quality Gardall fire safe, with steel interior and poured in composite insulation.
Almost all gun safes consist of an outer steel shell lined on the inside with drywall, and no inner steel. Most use Type X drywall which contracts and breaks into pieces during a fire. Drywall is a poor insulator compared to the poured-in composite. That causes manufacturers to misrepresent their fire ratings. Photo on right is a typical gun safe – fabric covered drywall, no inner steel.
Most quality fire safes have an Underwriters Laboratories fire rating of one or two hours. These safes have been tested independently under standard procedures at temperatures up to 1700 and 1800 degrees, respectively. Some have also undergone a 30 foot drop test. Imported units are normally tested according to Korean or Japanese standards, which are similar to U.L.’s. Gun safes will rarely pass U.L. tests so most manufacturers and importers do their own tests, or they make up numbers without testing. They often mislead consumers by mentioning “U.L. Rated”, but the U.L. rating they refer to has nothing to do with fire.
There are all kinds of ways to cheat when you test your own product. I have been told by people who worked there, that one company actually caulks the door shut during their fire test. Another way to fudge is to put the inside temp recorders in the bottom of the test unit where temps are lowest. Putting some kind of thermal barrier in front of the safe during the test also works well. For instance, remember how effectively even a sheet of paper blocks radiant heat coming off a camp fire.
If you want to protect papers or cash in a safe with the very best fire ratings available, you really should not get a gun safe. If a gun safe with inner steel and poured-in composite makes sense to you, look at Graffunder safes or Amsec’s BF series.