In my last blog about vault doors, I mentioned the ridiculous fire ratings that some manufacturers claim to have, based solely on how much drywall insulation they use when their doors have never been tested. Now consider the seals used between the doors and frames.
To see the importance of seals on vault doors read my last few postings about gun safes. Look at the test data that shows how poorly most of them (all of which use a single heat-expanding seal) perform – how heat and smoke can infiltrate the safe before and after the expanding seal actually expands. The insulation in gun safes creates a positive steam pressure, because of the small confined interior space, to help push out the really hot air and smoke. This phenomenon will not occur with a walk-in vault because the interior space is so large. So an effective cold seal, in addition to an expanding seal, are even more important on a vault door than on a safe. And yet most vault door manufacturers use a single, expanding type seal.
American Security vault doors are built and sealed the same way as their BF safes, the safes that did so well in the fire test. It is logical that their vault doors will work the same way. I suspect that Fort Knox vault doors would perform in a similar way too because they have both cold and heat expanding seals.
When you look to buy a vault door, do not trust any claim the manufacturer makes about a “fire rating”, unless it has been tested and certified by U.L. The best you can do is to get one in which the door fits tight and there are two kinds of seals.