What Are Safe Fire Ratings? A Locksmith Explains.

UL Fire Rating Label
UL? KIS? JIS? 30 minute? 1hr? 2hr? Drop test? What do all of these safe fire rating classes mean?

A safe fire rating is a rating indicate how long the internal content of the safe will remain below 350°F (paper begins to combust at 450°F). There are several variables to safe fire ratings: the certifying agency used, external temperature the test was performed at, how long the safe will stay below 350°F, and will the safe survive a fall should the floor collapse in a fire.

Underwriters Laboratories (UL) – UL Fire Ratings Explained

UL is the global agency that offers standardized testing for companies who want to substantiate product claims. It’s the Gold Standard of rating systems, recognized and utilized worldwide in product manufacturing.

When it comes to safes, there is one UL fire rating, and that is the UL 72 Standards for Tests for Fire Resistance of Record Protection Equipment. The UL 72 safe fire rating test results in a safe receiving a fire class rating of a temperature and a length of time. “Class 350 – 1 HR” then is a UL safe fire rating that keeps the content of the safe less than 350°F for 1 hr at a given external temperature.

Most safes will be UL Class 350°F fire rated, “Class 350 – X Hr”, where ‘X’ is the length of time for which the safe is rated. This rating is designed to protect paper documents.

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Other fire ratings include UL Class 150°F – X Hr (to include things such as computer disks and photos) and UL Class 125°F – X Hr rating, to include floppy discs. You may find these fire ratings on data storage safes and media storage safes. These two ratings also contain a relative humidity rating, not to exceed 85 or 80% relative humidity respectively.

When you see these UL Fire Ratings applied, you can be assured that your safe has met the strongest standards of testing.

UL Fire Rated Safe Classifications

Fire Class Ratings: Time and Temperature
UL Class Fire Rated Time External Temperature Maintained
 Class 350 – 4 hr
Formerly Class A
4 Hours 2000°F
 Class 350 – 2 hr
Formerly Class B
2 Hours 1850°F
 Class 350 – 1 hr
Formerly Class C
1 Hours 1700°F
 Class 350 – 1/2 hr
Formerly Class E
30 Minute 1550°F

UL Fire Ratings for Safes are the gold standard, check out our article on this safe caught in a California fire and see How Important Are UL Fire Ratings?

The UL Fire Rating Testing Process for Safes

So what are these tests? How are they conducted?

Safe’s Fire Endurance Test

For the fire endurance test, heat sensors and paper are distributed evenly in the safe. The safe is exposed to a uniformly distributed fire that quickly rises to a given temperature based on the desired rating, and the safe must maintain an internal temperature at or below the desired temperature for the amount of time required for the rating.

Longer fire ratings also require higher the external temperatures. So higher fire ratings are more difficult to achieve than just reaching an increased set temperature exposure time.

Once cooled, the safe is opened and examined for usability, heat damage, locking mechanism function, etc.

Safe Explosion Hazard Test

The safe is locked in a preheated furnace set to 2000°F. This temp is maintained a specific length of time (30 minutes for a 1-hr fire rating is an example)

If it doesn’t explode, the safe then cools inside the closed furnace. Once cooled (this can take days), it’s opened and examined for usability, as above.

30′ Impact Test

Safe’s Fire Impact Test (Manufacturer’s Option)

For the safe’s impact test, the safe is placed in a furnace, following the same time and temperatures used in the Fire Endurance Test.

At the end of the required time in the furnace, the oven is turned off, and within 2 minutes from the fire being turned off, the safe is dropped 30 feet onto a pile of loose bricks over concrete.

It’s brutal. But if your safe was on the third story, and the floor burnt through, you’d want to know if you have any protection. But wait … there’s more …

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When the safe has cooled sufficiently to handle, it’s then turned upside down, and again goes through the testing procedure. Then it’s allowed to cool, inside the closed furnace. Then it’s inspected for usability. Again.

Many of the fire safes from one of our favorite manufacturer, Hollon, (see Are Hollon Safes Good Safes) have survived this test.

In the UL safe fire rating system, the safes must be tested again after one year of manufacturing to maintain their rating, and the rating is good for comparably built safes down to 50% volume smaller or up to 50% volume larger.

Other Safe Fire Rating Systems

KIS / KSG-4500 Safe Fire Rating Decal
Testing to achieve a Safe’s UL fire rating is no small affair, and it can cost more than $60,000 (plus the costs of the safes scarified to the testing ovens). In many cases safe manufacturers just can’t pony up that kind of money for each safe they have to test, especially for new manufacturers with limited funding.

Because of this, safe manufacturers may hire an independent company other than UL to perform their safe fire ratings.

With many safes being manufactured in Asian countries, a popular safe fire rating is the KIS fire rating. The KIS fire rating is the Korea Industrial Standards rating. The KIS fire rating involves similar tests to the UL Fire Rating, but with slightly different standards. They still serve as a valuable tool in determining a safe’s fire protectivity, if you understand what the testing involves.

Similarly, there is a JIS Safe Fire Rating out of Japan (EN 1047). This also typically includes a drop test.

Intertek ETL Testing Lab Safe Fire Rating Decal
And another popular testing facility is the ETL-Intertek laboratories. They’ve been in business for over 100 years. They do all of their fire rating tests at 1200 degrees.

Whether it’s UL fire rating, KIS Fire Rating or the JIS fire rating, standardized testing is the best way to ensure the safe will succeed in its fire rating.

Manufacturer’s Fire Rated Claims

Many manufacturers will do their own testing and give their own rating. Be wary of these! This is an internal company test with no oversight, and may in fact only be a guess or they conduct the test under the most favorable conditions (like slowly over 40 minutes, which doesn’t really give you an accurate assessment). They may also reduce the external temperature to as low as 1200°F.

Check out our article on Getting the Best Fire Rated Safe – many safes that have had their own testing, don’t achieve even close to the time they are “fire rated” for.

While an internal fire rated safe may be perfectly capable, do your research and try to determine how the fire rated tests were performed.






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