The D.C. Fire Department's Hazardous Materials Unit has uncovered evidence that numerous high-voltage transformers located in Smithsonian Institution buildings on the Mall are leaking PCBs.

Other sources familiar with the institution's electrical system said circuit breakers that should afford protection are themselves a fire hazard.

The increased risk of fire is especially critical in a Smithsonian building because a PCB blaze, and the cancer-causing chemicals it would produce, could contaminate forever many national heirlooms and close the structure for years, officials said. The danger to firefighters would be so great, fire officials said, that they might not go inside to battle an electrical blaze.

After the fire department's June 27 visit, Lt. Pat Walsh wrote in a log of the Hazardous Materials Unit: "Initial evaluation of situation at American History Museum, if fire involving transformer in a vault is reported, entry into the smoke is made at severe risk."

In an interview, Walsh said, "Only for the immediate rescue of people would I send someone into the smoke . . . . The people at the Smithsonian can't possibly recognize the danger or they wouldn't leave it the PCBs there."

The Environmental Protection Agency said yesterday that it has scheduled an emergency inspection of the Smithsonian's 57 PCB transformers to see if they meet federal standards for continued operation. EPA experts said the PCBs themselves pose no immediate danger to visitors because they are in areas not accessible to the public.

The Smithsonian's fire and safety director, Edward R. Sniechoski, said in an interview that the transformers are continuously inspected and meet all EPA standards, but that if any defects are found they will be repaired. He characterized the apparent leaks as "weepage" or "seepage," and said they are normal and are not a hazard.

EPA officials said PCB transformers can be used only if they are "intact and nonleaking." Generally, an EPA expert said, if there is enough fluid to "drip," containment measures must be taken and "servicing initiated in 48 hours."

EPA enforcement officials said yesterday they would not comment on the situation at the Smithsonian until they have made their own inspection. They would not say when the inspection is scheduled, but it could be as soon as next week.

In an unrelated move yesterday the EPA -- citing the danger to firefighters -- released new regulations that will require removal of all high-voltage PCB transformers -- such as those used in the Smithsonian -- by Oct. 1, 1990. By that same date, low-voltage PCB transformers will have to be modified to give additional protection against fires.

Replacement transformers are expected to cost about $70,000 each. Sniechoski said the Smithsonian is working on a replacement schedule. However, the institution's $180 million budget request for fiscal 1986 does not include any money for replacements.

"It takes a large project because museums don't just close down . . . . It's quite a major planning task," Sniechoski said. He said the Smithsonian realizes that much of the concrete flooring where the PCBs have spilled will have to be torn out and replaced to meet EPA regulations.

PCBs, or polychlorinated biphenyls, belong to a family of organic compounds known as chlorinated hydrocarbons. Produced in the United States between 1929 and 1977, they were widely used as coolants for electrical transformers because of their fire-retardant properties.

When PCBs burn, however, they produce other more deadly chemicals, including dioxin 2,3,7,8,-TCDD, which the EPA describes as "one of the most toxic substances known to man." It can affect human reproduction, and animal tests have shown it causes liver, mouth, adrenal gland and lung cancer.

A fire in a state office building in Binghamton, N.Y., on Feb. 5, 1981, in which a PCB transformer split open from heat, has cost $28 million to clean up and the building is not to reopen until early next year.

David Rings, the state's executive coordinator for general services, said yesterday that almost everything in the building, including draperies, furniture and typewriters, had to be destroyed because of contamination.

According to the Hazardous Materials unit's Walsh, the fire department's June 27 visit was prompted by a Smithsonian employe who called him and said "there was a mess down at the Smithsonian." Walsh said that while on a tour of transformer vaults, or rooms, in the Musuem of American History, "We were kicked out" by a Smithsonian official. He said Andy Wilson of the Smithsonian's fire prevention branch later called to ask "what the hell were we doing there."

Sniechoski said the D.C. Fire Department, which would battle any fire in a Smithsonian building, does not have jurisdiction over the institution and should have contacted his office if it wanted information about the transformers or desired to tour the building.

Walsh said that a list maintained by the fire department of PCB transformers in government buildings showed a single PCB transformer in the Smithsonian, located in the castle.

The General Services Administration lists all PCB transformers in government buildings, but does not have jurisdiction over the Smithsonian, which reports only to its own governing board.

"It never entered my mind to go down there to cite them," Walsh said. "I only wanted to locate PCB oil so if there's a fire we can warn firefighters to stay away."

Before leaving the building, the seven firefighters saw about half of the 23 PCB transformers in the Museum of American History and noted puddles of the transformer coolant being collected in drip pans and collecting on the concrete floor.

Walsh said the disposal of materials used to clean up the puddles of PCB-laden coolant appeared to be "haphazard." In addition, Walsh said, he was told that a 55-gallon drum -- used to store PCB coolant removed from a transformer after the substance leaked into the area containing a 13,200-volt feeder line -- had leaked onto the concrete.

A large containment barrel holding the ruptured drum, and two 55-gallon barrels, one with waste PCB coolant and the other with contaminated rags that had been used during the past 1 1/2 years, were stored in a high-voltage vault next to the transformers, according to fire and Smithsonian officials.

Fire department Battalion Chief Ralph Richardson, who accompanied Walsh to the Smithsonian, said most of the 10 to 15 transformers he saw "were in deplorable condition."

Sniechoski said an immediate cleanup of areas toured by the firefighters was initiated the same day. The waste PCB materials and cleanup rags were removed from the building July 2 by a licensed waste disposal firm. Although firefighters toured only part of one building, sources familiar with the Smithsonian's plants said that other transformers are in similar condition.

A total of 57 PCB transformers are in Smithsonian Institution buildings on the Mall. Fifteen PCB transformers are located in the Musuem of Natural History, six in Arts and Industry, three in the Smithsonian castle, two in the Freer Gallery, four in the National Air and Space Museum and four serve the Museum of American Arts and the National Portrait Gallery.

Smithsonian buildings have two types of high-voltage transformers: those that take power from 13,200-volt feeder lines, reduce it to 480 volts and distribute it to other transformers, and those that convert the 480 volts to 110 and 220 volts.

The Hirshhorn Museum and Sculpture Garden is served directly by the Potomac Electric Power Co.

In addition, a source said, "Every building has defective circuit breakers," which "may not trip under overload conditions." These are usually a protection against fires.

A 173-page report completed in June for the Smithsonian by Substation Test Co., an electrical contractor, said there "are some defective circuit breakers," including at least 14 of 44 circuit breakers in the Museum of American History.

In the Museum of Natural History, the three main switches on the 13,200-volt feeder lines are "burned black from overheating," and corroded in the open position, sources said. They said the power could not be shut off even with three people "hanging" from the switch, known as a bust bar.

An expert with Harry Alexander Inc., electrical contractors, said yesterday, "Anytime you cannot shut down any protective device to a piece of equipment of any type, that's a potential hazard, because that was the main reason it was put there . . . . The device it's protecting could burn up and there's a chance it could start a [larger] fire."

The Binghamton fire started in switching gear located in the room with PCB transformers. About 180 gallons of PCB coolant spilled and burned in the New York fire; the largest transformer at the Smithsonian is filled with 565 gallons of PCB coolant, known as askarel.

John Payne, an electrician hired temporarily by the Smithsonian and the man who notified the fire department, said he was concerned that all safety precautions were not being followed. He said many electrical panels in the museums have been covered by walls and exhibits, which would also hamper efforts to shut off electricity during a fire.

Payne has been notified that he will be removed from his job on July 20. His termination letter cited poor working habits and being off the job without permission, but Payne said he believes he is being fired because he called in the fire department.

Sources said regular inspections of the transformers didn't start until about 18 months ago. When workers began to clean up what a source characterized as "15 years of neglect," dead rats were found stuck in gelatinous pools of PCB waste under the transformers.

Payne and Smithsonian officials said the transformers are now checked frequently and specially fabricated drip pans have been placed under almost all of them.

Sniechoski said the Smithsonian prides itself on its working relationship with the fire department, but added that the PCB matter is "not the problem it was made out to be."

He denied that the transformers have not received regular maintenance, saying that Substation Test Co. had a contract to perform the maintenance until recently. A spokesman for Substation said its contract covered only specific repairs on certain transformers, and other general electrical work.

Payne, who said he may challenge his removal, said that since the fire department visit, "Everybody is walking around with books that say PCB on them. They're all reading them now."