How does a fireproof filing cabinet actually protect documents in a fire?

The protection comes from the space between the two steel walls: a thick insulating layer of gypsum, concrete aggregate, or vermiculite that absorbs heat slowly and releases moisture as steam, keeping the interior below the temperature at which paper chars (451°F) for the rated time duration — 1 hour or 2 hours depending on the model. The double-wall construction is what makes these cabinets so much heavier than standard file cabinets. Browse UL-rated commercial fireproof cabinets at FindOfficeFurniture.com or call 888-719-4960.