Understanding UL Classifications for Fireproof Safes

A fireproof safe has an insulated body and doors designed to protect the safe contents from high temperatures or actual fire. In addition these types of safes may be rated for impact resistance should the safe fall during a fire. Underwriter Laboratories (UL) in the United States is a world leader in both the writing of standards and the actual testing of safes.

Under the UL classification system fireproof safes can be given one of three classifications with the classification given dependent on the maintained internal temperature and internal humidity when subjected to at a designated furnace temperature. Dependent on the safe’s construction and the test parameters the UL time rating label indicates the time the safe can maintain the internal temperature and humidity at the furnace temperature for which the safe is being tested.

The three classes UL uses to classify fireproof safes are Class 125 (maintains an internal temperature of 125 degrees F and humidity not exceeding 80%), Class 150 (maintains an internal temperature of 150 degrees F and humidity not exceeding 85% ) and Class 350 (maintains an internal temperature of 125 degrees F and humidity not exceeding 85%) and are used in conjunction with UL time rating labels. UL time rating can be for half an hour at a furnace temperature of 1700 degrees F, one hour at a furnace temperature of 1850 degrees F, two hours at a furnace temperature of 1850 degrees F, three hours at a furnace temperature of 1920 degrees F or four hours at a furnace temperature of 2000 degrees F. Having three different internal temperature classifications combined with five time ratings allows fireproof safes to be classified according to the type of records being protected.

Fireproof safes can be separated into two main categories, data safes designed to protect computer media and document safes designed to protect paper products. In the event of a fire a Class 125, 1 hr UL fire rated safe would hold an internal temperature of 125 degrees F at a humidity less than 80% and could be relied on to protect computer diskettes for one hour in fires where temperatures do not exceed 1700 degrees F. The U.S. Department of Commerce, National Institute of Standards and Technology test report FR4009 recorded the temperatures reached in a controlled house fire. The maximum temperature recorded was 1350 degrees F which is well below the 1700 degrees F used in UL testing of fireproof safes. A Class 150 classification would be suitable for protecting microfiche, cassette tapes, microfilm etc.

Home safes are typically smaller than those used in business, but depending on individual requirements business safes may be suitable for home use. Floor safes are also popular in homes and business and when installed in concrete can provide excellent fire resistance. In the majority of cases a Class 350 fireproof safe would be suitable for the majority of homes. Typically a Class 350 fireproof safe with a UL half hour rating has been heated in furnace to 1550 degrees F and the interior of the safe has maintained a temperature of no more than 350 degrees F for a period of half an hour. This class of safe is best used for the securing paper products.

The majority of business safes are used to secure cash, paper documents and proprietary files. For businesses the industry standard fireproof safe is a UL Class 350 1 hour rated safe. Because paper begins to burn at 420 degrees F and most fires are extinguished within twenty minutes a Class 350 1 hour rated safe will provide the majority of businesses with the fire protection they require. Cash and valuable papers will not burn because of the built in safety margin between the flash point for paper, 420 degrees, and the interior temperature of the safe which will not exceed 350 degrees for at least an hour.

Whether you are looking for a safe for home or business using the UL class ratings in combination with the type of products to be protected will give you a good start in selecting the fireproof safe to suit your needs.