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Fire Ratings

Fire Ratings Explained

The National Fire Protection Agency (NFPA) reported 383,500 home fires in the United States, accounting for $5.5 billion of property damage.

The following information applies to both Fire Rated Safes and Burglar/Fire Rated Safes. Remember that a Fire Safe without a Burglar Rating is not recommended for Burglar Resistance. If you need both Fire and Burglar resistance, always consider a Burglar/Fire Rated Safe over a Fire Rated safe only.

There are many types of Fire Ratings. SafeManufacturers will provide testing from a variety of sources such as:

  • Private Laboratory Testing
  • K.I.S. (Korean Industrial Standard) Fire Test
  • U.L. (Underwriters Laboratory) Class of Fire Protection

There are other Fire Ratings not mentioned, such as various European fire rating standards. Many manufacturers hire a reputable private laboratory to test their fire or burglar/fire safes for a fire rating. Safe's made in Korea usually have the K.I.S. Fire Test, which is a Korean Fire Lab test. The most thorough and recognized fire test is the U.L. Class of Fire Protection.  (see description below)

Private Fire Label Testing:

Fire Ratings

Private Label Fire Testing is where a safe manufacturer hires an Independent Testing Laboratory to test their safe for a specific fire rating time period. Like the Korean or Underwriter Laboratory fire tests, the Independent Laboratory places heat sensors inside the safe. The safe is placed in a burn chamber. The temperature is brought up to between 1350-1750 degrees F. Once the desired temperature is achieved, the Independent Laboratory starts timing how long the temperature stays below 350 degrees F. If the inside temperature stays below 350 degrees F for 1 hour or more, then the fire rating is 1 hour. Same for 1.5 hours, 2 hours, and so on. The importance of the 350 degrees F is that paper (or money) will start to char at approximately 387 degrees and burst into flames at 451 degrees F. For these reasons, maintaining a temperature below 350 degrees F is what all fire tests look to achieve.

Korean Industrial Standards (K.I.S.) Fire Tests:

Gardall FB1212 Fire Rating

Here is an example of how the K.I.S. Fire Test is conducted on a safefor a 2-hour fire rating with an Explosion Test and a Fire Impact (drop test):

K.I.S. (Korea Industrial Standards) rated by the KSG-4500 fire resistance tests. Papers and valuable documents will remain protected by the rating standards against fire, explosion, and drop impact during fires.

  • A Fire Safe is tested for 2 hours in a furnace with the temperature rising to 1850° F.
  • Explosion- Heated in a furnace to 1852° F in 10 minutes, continued at temperature for 30 more minutes.
  • Fire Impact- Subjected to standard fire exposure for 45 minutes, dropped 13 feet, returned to furnace upside down, reheated 1 hour.

Safe'swith the K.I.S. or a Private Laboratory Test still provide excellent fire resistance. However, the U.L. Class of Fire protection is recognized as the most complete fire testing today. If you are on a budget, we recommend you considering at least a 1-hour fire rating (minimum) to ensure ample protection for your documents or valuables.

U.L. Classes of Fire Protection

U.L fire rating of the Gardall Burglar safe

Underwriters Laboratories established five fire-resistant classifications for record protection. These classifications are based on the type, length, and severity of the test given each classification.

The classification ratings are:

  • 350-4 hour
  • 350-2 hour
  • 350-1 hour
  • Insulated record container 350-1 hour
  • Insulated record device 350-1 hour

3 Tests for Fire Protection

The Underwriters Laboratory provides three basic tests for the fire resistance of record protection equipment.

These are:

  1. Fire Endurance Test
  2. Explosion Hazard Test
  3. Fire Impact Test

    Equipment in classes A, B, and C are subjected to all three tests. Equipment in classes D and E do not take the fire impact test.

    Fire Endurance Test

    The Fire Endurance test measures the degree of resistance that the safe has to temperatures determined by standardized fire exposure conditions.

    In preparation for the fire endurance test, the safe is placed in a cold furnace so that all exterior surfaces will be exposed except the bottom. Heat measuring apparatus is installed in the interior of the safe, and papers are loosely distributed to contact all interior surfaces. The safe doors are closed and locked, the furnace is shut, and the fire is started.

    The heat of the furnace is gradually increased according to set standards of time and temperature. The gas and air supply is adjusted carefully so that the fire is well distributed over the sample, and thermocouples symmetrically distributed in the furnace accurately record temperatures so that the test standards are maintained.

    The test sample remains in the furnace for the period required for the desired classification. When the time has expired, the fire is extinguished, and the sample is allowed to cool without opening the furnace. Here is the test times and temperatures for the various classifications:




    Class A

    4 hours

    2000 degrees Fahrenheit

    Class B

    2 hours

    1850 degrees F

    Class C

    1 hour

    1700 degrees F

    Class D

    1 hour

    1700 degrees F

    Class E

    30 minutes

    1550 degrees F


    After the test sample has cooled, it is opened, and the contents and interior surfaces are examined. The records must still be usable, and the interior must show no signs of undue heat transmission. At no time during the test must the temperature inside the safeexceed 350 degrees F. The general security of the safe is also examined. The records are considered "usable" if they can be handled without breaking and are decipherable by ordinary means.

    Explosion on Hazard Test

    The Explosion on Hazard Test determines whether or not the design of the safeprotects it against explosions in case of sudden intents heat exposure. If the safe construction is faulty, the sudden high temperature will cause hydrogen-air-stream mixtures in the insulating material to explode and rupture the insulation and safe walls. This rupture will destroy much of the safe'sresistance to fire.

    The test for an explosion is relatively simple. The empty, closed furnace is pre-heated to 2000 degrees F. The furnace is opened, the test sample is inserted, and the furnace is closed again for 30 minutes while the fire is maintained at 2000 degrees F. After the test, the sample is allowed to cool until it can be handled. If no rupture of the insulation can be found, the sample passes the test.

    The Fire Impact Test

    The Fire Impact Test measures the resistance of a safe to impact when in a heated condition. The test simulates a safefalling three floors to the basement of a burning building, then lying in the burning embers until cool.

    During the test, the sample is placed in a furnace, and the fires are lighted. The time and temperature follow the same standards as for the fire endurance test for the length of time determined by the classification desired. At the end of the required time in the furnace, the fire is extinguished. The truck and sample are hoisted so that its bottom is 30 feet above a riprap of brick on a heavy concrete base, then dropped. The drop is made within two minutes of the time the fire is extinguished.

    Pretty rough? Yes, but the test isn't over yet! When the safe has cooled sufficiently to handle, it is inverted, reinstalled in the furnace, and again subjected to the standardized time-temperature conditions for a period determined by the classification desired. After the time is over, the sample is allowed to cool before the furnace is opened. When the doors are forced open, the records must be in usable condition.

    The Underwriters' Laboratories Inc. is the most highly respected testing and grading agency in the world. Their testing label of whatever classification means that the safehas passed the highest standards they have established for safes. Underwriters' Laboratories integrity through the years guarantee to the consumer that no portion of any test which establishes the grade has been slighted in any way.

    Caution: Read the Label

    On occasion, a particular manufacturer or another association of manufacturers may attach their grade label to their equipment. The customer should be aware that such a label on a piece of equipment does not necessarily mean that the equipment is comparable to another piece of equipment that bears the Underwriters' Laboratories grade label.