1. "UL" Fireproof RatingsThe UL rating for a fireproof safe is one of the best-known ratings in the home security world. In the United States, the Underwriters Laboratory specifies the level of protection a safe can offer when exposed to fire. The lab exposes a safe to various conditions that evenly heat all sides; and depending on how long the contents last without damage, it will be rated according to three standards:
- Class 125: Suitable for computer disks and digital media.
- Class 150: Suitable for magnetic tapes and photographic film
- Class 350: Suitable for paper products
2. UL Fire Endurance RatingsThe Underwriters Laboratory also measures how long a safe can structurally hold up in a fire. For a fire endurance test, a safe is placed in a cold furnace so that every side heats equally. Then the heat in the furnace is gradually increased until the safe is damaged. Some safes will include the length of time the container can withstand heat directly on the product, while others will use the following alphabetic rating:
- A: Can withstand up to 4 hours at 2000 degrees
- B: Can withstand up to 2 hours at 1850 degrees
- C: Can withstand up to 1 hour at 1700 degrees
- D: Can withstand 30 minutes at 1700 degrees.