(FORTUNE Magazine) – FIRE, FLOODS, earthquakes, and hackers can destroy a company's critical computer records. Ed Coggins, a group vice president at Total Assets Protection Inc., a computer security consulting firm in Arlington, Texas, draws the logical conclusion for managers. ''Corporations,'' he says, ''have to protect against what they can't afford to lose.'' A company's first line of defense: storing duplicate payroll information, customer lists, and other computerized data someplace far from the data-processing center. About 200 U.S. companies take in revenues of about $50 million a year providing so-called off-site computer data storage, according to Richard Drutman of Arcus Inc., a 15-year-old company that owns seven vaults in the West and Southwest. Though the industry has been around since the early Fifties, when a few companies constructed combination bomb shelters and storage areas, it is now growing fast and attracting big players with new ways of storing data. Since corporations need to replace data almost as soon as they are lost, security experts say that managers should look for off-site storage firms that are close enough to provide backup tapes within hours, yet far enough away to avoid, say, the same fire or storm or sabotage that caused a crisis. A storage company should have unmarked courier trucks to shuttle magnetic tapes, disks, and even paper documents 24 hours a day. Vaults should be fireproof, well guarded, and temperature and humidity controlled. Data could be lost on tapes stored where it is hot and humid. As a further security measure, managers should require contracts that forbid the off-site company from revealing the client's name. Some companies, such as National Security Centres of Bellevue, Washington, offer small high-security lockers in which a home computer user might stash his disks. According to Total Assets Protection, monthly storage costs range from 30 cents to 70 cents per cubic foot. The Paine Webber brokerage firm will spend around $100,000 a year to store and move tapes in and out of a Dataport Co. storage area as big as three city blocks, ten stories below Manhattan's World Trade Center. Florida Informanagement Services, a cooperative data-processing center that keeps records for 90 savings and loan companies mostly in the Southeast, pays $1,500 a month to store nearly 1,000 tapes at a new vault run by Data Protection Inc. in Orlando. Corporate giants getting into the business include Digital Equipment Corp., which offers off-site storage for customers, and AT&T. The telephone company hopes to transmit data from clients to off-site locations over high-speed fiber-optic cable, eliminating the need for couriers. Dataport is working on the same thing with a joint venture of Merrill Lynch and the Port Authority of New York and New Jersey. Sungard Recovery Services, based in Wayne, Pennsylvania, and Comdisco Disaster Recovery Services, a subsidiary of Comdisco, a Chicago computer-leasing company, offer clients off-site hardware in case disaster hits a company's computers. Because they are all wired and ready to run, these places are called hot sites.