People often use fireproof safes in homes to store important documents such as birth certificates, vehicle titles and invoice receipts safe from fire. To make safes fireproof, liners are placed around the edge of the door, where the door makes contact. The liners are called boiler gaskets, installed by applying UL tested intumescent caulk that ensures a good seal to prevent fire, smoke and moisture from entering the safe. To ensure the safes are fireproof, the manufacturer puts them in an oven, the ovens are set to 1,200 degrees Fahrenheit and monitor the interior temperature. When the interior of the safe reaches 350 degrees Fahrenheit, the test stops and the safes report how long it took for the interior to reach 350 degrees Fahrenheit. Once the safes are tested, the company will classify them as “Class 350-1,” the “350,” based on how hot the interior became during testing. “1” indicates the time it took to get there; in this case it took an hour. If it lasted two hours, a “2” would replace the “1” in the class grade. It also comes in many sizes, from a small tissue box to a large gun.