A good fireproof safe—and all of the models we recommend—sports a rating from an independent testing laboratory. Our picks have been put under fire (literally) by either UL or Intertek. Both labs test fireproof safes to determine how long they can withstand extreme heat and keep their contents below 350 degrees Fahrenheit. That threshold is below the point at which something like paper autoignites or bursts into flame simply due to the heat of the air around it. (You can thank Ray Bradbury for giving the world Fahrenheit 451 as a shorthand for remembering the autoignition temperature.)
How hot a safe can get and how long it can withstand that temperature before it fails depends on the safe, so look for one rated for the level of protection that makes you comfortable, knowing that safes rated for hotter and longer conditions are often more expensive. Our top pick, the Honeywell 1114, is UL and Intertek rated to keep its contents below 350 °F for one hour at temperatures of up to 1,700 °F, but others can be rated for 30 minutes up to 1,462 °F or for two hours up to 1,850 °F.
The notable factors for a safe’s survival then become how hot a house fire gets and how quickly, which is tricky because house-fire conditions are so variable. When trying to nail down the typical temperature of a house fire, I found data that varied by hundreds of degrees. Most guidance says that the average house fire burns at upwards of 1,000 °F, and one study found that the temperature in a 1:1-scale fire-experiment laboratory reached a maximum of 2,192 °F, well exceeding any fireproof safe’s maximum temperature rating.
“These safes are likely tested to a standard fire test, which enables consistent replicable test results,” explained Brett T. Lacey, Colorado Springs Fire Department fire marshal, in an email interview. “Fires in the real world can be so varied and difficult to replicate, generally with higher temperatures that cause unpredictable performance confirmation.”
When it comes down to it, early intervention is the key to preventing your safe from experiencing the heat exposure that will cause it to fail. The National Fire Protection Association has established a set of standards that all career fire departments in the United States strive to meet. It states that fire departments should aim to get the first fire engine to the curb within 240 seconds of receiving the 911 call. Of course, variables such as staffing, traffic, and home accessibility can skew that number—but in general, help should arrive in a matter of minutes, giving your safe a better chance of surviving the blaze.
