Each Sentry fire safe model have been tested and rated either ETL certified or UL classified. These are ratings assigned by independent laboratories after rigorous testing. All Sentry fire safe products have been tested and the interiors remained below 350F in a typical* fire. Paper chars at 450F so these safes protect papers and many other valuables. You may want a specialized Sentry fire safe for rare coins, media, data and photographs.
A Sentry fire safe basically works to protect contents by keeping heat out. The insulation used contains encapsulated moisture which deters flames and cools the interior. The insulation is also designed to vent and not hold heat.
Specifically For Chests and Files:
Two elements in the design of the chests and file work together to protect the contents.
First, there are molded polymer housings which, when exposed to the heat of a fire, melt and essentially weld together, sealing the interior. A sealed interior provides better protection. Second, there is a Survivacast filling in the double walls which shields the contents from the heat of the external fire. This filling encapsulates water which turns to gas in a fire. An endothermic reaction happens...absorbing the heat.
Please note that the lifetime after fire replacement warranty means that Sentry will replace your safe if damaged - not the contents. Please insure anything valuable your store in your safe. Also in the rare case that your product would be damaged in a fire, you will need to pay the shipping for the new product.