The attic furnaces were made by now-bankrupt Consolidated Industries (formerly Premier Furnace Co.) and were sold under at least 30 different brand names between 1984 and 1992, the Consumer Products Safety Commission says. The agency issued a warning about the furnaces last autumn but has no way of knowing exactly where each of the units were installed--and thus no way to warn those property owners directly.

According to a CPSC spokesman, a modification that Consolidated Industries made to the furnaces in order to meet regional air-quality regulations also made them prone to failure. Fire officials say the furnaces have accounted for at least 100 fires over the past decade.

The latest blaze occurred Sunday in the South Bay town of Torrance. The fire began in the attic of a vacant condominium and caused $50,000 in damage. No one was hurt, a spokesman for the Torrance Fire Department says.