It started with an unusually warm wall outlet that was replaced in 1972, and ended two years later when Rosalind Hersh was awakened early one morning by the smell of smoke.

The guest bedroom was ablaze, the flames already blocking the hallway to another room where the Hershs' daughter lay sleeping. Unable to escape, Mrs. Hersh collapsed.

Firefighters saved her, but her husband and daughter died. The fire was blamed on faulty aluminum wiring.

"Nobody ever told us that aluminum wire was dangerous," she testified last week before the opening session of congressional hearings into the aluminum wire situation. "A time bomb had been built into our house and we didn't know it."

Rep. John E. Moss (D-Calif.) told his investigations subcommittee that 1.5 million American homes "may be facing an unnecessary and unreasonable risk" of fires from defective aluminum wiring, yet the aluminum industry is reluctant to publicize the problem.

Twisted wires, charred outlet receptacles and plugs, melted bits of cord and plastic fragments passed from hand to hand among subcommittee members as witnesses described their experiences.

"I didn't know we had aluminum wiring," said Frank Puckett of Dalton, Ga., whose family lost all its possessions in a fire last November that destroyed their 24-unit apartment building. "We feel lucky that we escaped without injury."

Former D.C. chief fire inspector Robert J. Kelly, who investigated the $1 million Georgia blaze as a private consultant, said it was probably caused by a failure at a connection between aluminum wire and a wall plug.

"Overheating occurs at loose aluminum wire connections when current passes through the connections," Kelly testified. "This overheating can cause fires. Loose connections can also cause incidents such as flickering lights, buzzing at switches or sparks coming out of (wall) receptacles."

Kelly noted that of 44 major fires in electrical service equipment that he investigated in Washington between 1968 and 1975, 31 involved aluminum wiring. "It was the problem in large cables and major building wiring centers, not just in private homes," he said. "The problem is national in scope, no doubt about it."

Electrical circuit breakers provide no warning in case of aluminum wire failure, he continued, because they are designed to warn only of overloading or short circuits. Loose or incomplete aluminum wire connections instead cause tremendous heat and arcing that does not interfere with the flow of current until the wire melts away or there is a fire.

The aluminum industry has consistently held that shoddy workmanship by installers is at the root of whatever problems homeowners have had with aluminum wire, and that property installed aluminum wiring is as safe as any other.

The majority of houses, mobile homes and commercial buildings with aluminum wire were built or rewired between 1966, when copper prices rose sharply, and 1973, when problems with aluminum wire began to receive publicity. The Consumer Product Safety Commission filed suit last October to require 26 aluminum "wire producers to inform homeowners in booklets and advertisements that wiring of that era may be hazardous.

The industry has blocked that suit in U.S. District Court in Washington with another suit in another court, the U.S. Court of Appeals, charging that the Consumer Product Safety Commission has no jurisdiction over aluminum wire.

Kaiser Aluminum & Chemical Corp previously obtained a federal court order that gagged the commission from discussing aluminum wire on grounds that aluminum wiring was not a consumer product. The jurisdictional question must be resolved before the suit against the 26 manufacturers will proceed.

Moss was careful to distinguish between "old technology" aluminum wiring which he said was unsafe, and "new technology" wiring installed since 1973 which he said was safe.Robert Nooman of the product safety commission, however, went further in his criticism.

The problem, he said, can still be found in houses where aluminum wiring was installed after 1973 and is stamped [WORD ILLEGIBLE] to indicate that "new technology" was used in those houses. "We don't really have enough data at this time to tell if they are useful," he said.

Background material supplied by Moss explained that chemical reactions between aluminum and oxygen in the atmosphere produces aluminum oxide, which does not conduct electricity. As the oxide forms on the wire, the flow of electricity is blocked and constructed to an ever-narrowing area, which causes heat that in turn speeds the process, eventually cutting off the circuit. The blockage is so narrow, however, that the current may arc cross it or break through in spurts.

This, the material indicated, is what causes lights and television screens to flicker and connectors to overheat. In addition, aluminum's physical characteristics tend to loosen connections, with the same result.

The "new technology= installations require special equipment and tools. "Residential wiring, however, is not usually installed by highly trained technicians using special equipment," Moss's information sheet noted.

Homeowners worried about aluminum wiring could give their houses a "quick fix" for $300 to $600, but if all wiring needed replacement the costs could reach $3,000, the statement continued. Replacing all "old technology" wiring systems with "quick fixes" alone could cost the nation as much as $900 million.

S. John Byington, chairman of the commission, told the subcommittee Monday that all of the estimated 1.5 million American homes equipped with aluminum wiring systems manufactured between 1965 and 1973 should be checked by an electrician for possible fire hazards.

Byington said that so-called "old technology" aluminum wiring systems "may malfunction at any time and create serious overheating and fires."

Asked what a homeowner with old technology aluminum wiring should do, Byington replied, "Call an electrician."

A pamphlet called "Do You Have an Electrical System With Aluminum Wiring?" is available free from the Consumer Product Safety Commission, Washington 20207, by calling the commission's toll-free hotline, 800-638-2666, or, in Maryland only, 800-494-2937.