A UL 72 rating is given to a safe based on the below three factors.
Classification: It determines the products that can be kept safe in this safe box. The three classes are:
Class 350: Protects documents and other malleable items
Class 150: Protects any item with magnetic tapes
Class 125: Only protects low-durable items such as compact or floppy disks
Duration: It determines how long material can withstand fire before its characteristics are compromised. The duration can range from 30 minutes to four hours.
Ratings: This factor is determined after several tests in the laboratory. The safes are tested to varied fire impacts, explosions, and fire endurance. A safe is kept inside a high-temperature oven for long periods, and the interiors are tested with humidity detectors. But as house fires are unpredictable, this factor may not be entirely accurate.