The last thing Jim worries about when he leaves his small engineering firm each day is the safety of his computer records. Not only does he back up his data onto DVD's faithfully each day, but he stores the DVD's in a fireproof safe left behind by the former owner of his building.

Unfortunately, Jim's enjoying a false sense of security. While his fireproof safe is fine for protecting paper files and even money, it isn't adequate for maintaining the critical temperature and humidity levels necessary for magnetic tapes, floppy disks, CDR's, or DVD's.

The average house fire reaches temperatures of about 1,200 degrees Fahrenheit. Paper chars at about 420 degrees and burns at about 450 degrees. By contrast, magnetic tapes, floppy disks, and other storage media can be damaged by temperatures above 125 degrees and by humidity levels above 80 percent.

As a consequence, manufacturers of fireproof safes have developed chests, files and safes specifically designed to protect computer storage media, as well as photo negatives, audio and video cassettes and x-ray films that share many of the same characteristics.

If you're looking for a container to safeguard such products, look for one that carries a Class 125 rating from Underwriters Laboratories for one-half hour or longer, up to a maximum of four hours. That means it will maintain an interior temperature below 125 degrees Fahrenheit and humidity below 80 percent when subjected to exterior temperatures ranging from 1,550 degrees (for the one half-hour rating) to 2,000 degrees (for the four-hour rating). Most products sold for use in the home carry the half-hour or one-hour rating.

For protection of valuable or hard-to-replace paper documents, look for a UL 350 classification. That means the chest, safe or filing cabinet will maintain an interior temperature below 350 degrees when exposed to temperatures ranging from 1,550 degrees (for the half-hour rating) to 2,000 degrees (for the r four-hour rating).

These UL ratings also signify that the product has survived UL's combined explosion hazard/impact test. In this test, the product is subjected to 2,000-degree heat for 30 minutes, dropped 30 feet onto a riprap of broken bricks and concrete, then reheated to 1,550 degrees for 30 more minutes. If it doesn't explode, it passes the test.