Metro's subway cars should have metal seats and metal interiors to improve their resistance to fire, D.C. Fire Chief Norman Richardson has told the National Transportation Safety Board.

Richardson's comments came in a letter that was made available at a board hearing on the fire safety of the Nation's rapid transit systems.

"My main concern is with the design of the cars," Richardson wrote. He said that the seats of the cars are made of neoprene, which can be ignited by burning newspapers, and the interiors are constructed of polyvinylchloride, a plastic that emits highly toxic fumes once it is on fire.

Concern about fammable materials on subway cars was one of many safety issues that fire chiefs and transit officials from across the country discussed yesterday in the first of two days of hearings.

Richard Best, of the National Fire Protection Association, said that considering the prevalent use of combustible materials in modern subway cars, inadequate means of egress and the lack of automatic fire detection and fire extinguishing systems in many rapid transit systems, the passengers on a fully loaded train may not have time to exit to safety in the event of a fire.

"Until these problems are corrected, the possibility of a major life-loss from a rapid transit fire continues."

Safety board chairman James B. King and Andrew Casper, San Francisco fire chief, led a tour of the Washington Metro system in the morning yesterday. Among other things they pointed out:

The lack of an under-car sprinkler system to extinguish blazes before they grow. Most non-arson transit fires start in equipment under the car or in trash along the tracks.

The lack of any signs, either in Metro's stations or on its cars, telling people what to do in the case of emergency or how to evacuate the train.

The issue of evacuation instructions is an old one at Metro. Lawrence Engleman, Metro's fire safety coordinator, and other Metro officials have said frankly that Metro does not want to tell people how to get out of the cars, and others in the transit business agree with that view.

"It's a last resort" to evacuate people from the car to the track, Engleman said. Metro first tries to pull a stricken train into the nearest station. then tries to evacuate people to another train. An evacuation of a fully loaded train in the tunnel to another train, however, can take as long as an hour -- far longer than it takes a fire to become incandescent.

Metro's plans are for people to evacuate through the end of the car, under the supervison of either the train operator or other Metro personnel brought to the scene.

The side doors to Metro's cars -- the ones everybody normally uses to get on and off -- can be opened from inside the car once an advertising panel is removed. That simple process, however, is known only to a few insiders and was demonstrated for King, Casper and a number of television cameras yesterday by D.C. Battalion Fire Chief Gene P. Stewart, who is the department's liasison officer to Metro.

Adding to the problem of a sidedoor evacuation are the facts that the walkways along the tunnels are only wide enough for one person. Furthermore, the third-rail pickup-shoes are located immediately under the side doors, and they look just like steps. In fact, they carry 750 lethal volts even when not in contact with the third rail.

The safety board's interest in rail transit fire safety was pricked on Jan. 17, 1979, when a San Francisco Bay Area Rapid Transit train caught fire in the long tube under San Francisco Bay. All the passengers were evacuated safely, but an Oakland fireman was killed and it took the San Francisco fire department seven hours to bring the blaze under control.

The BART cars contained seats made of polyurethane, a highly flammable plastic that was replaced on Metro's cars with less flammable neoprene before they were put in operation. However, polyurethane seats remain on some older Metro buses.

In addition to the question of materials, the BART fire pointed to the need for joint training of transit authority and fire department personnel and strong back-up communication systems.

Metro General Manager Richard S. Page has met with the D.C. fire department and other area departments in an attempt to improve communications, markings in tunnels and other matters.

Page said yesterday that the question of placards in the cars and in the stations "is under review." He said he had not heard of Richardson's suggestion to replace the neoprene seats with metal seats.

Also at issue with the safety board is the lack of national standards or federal regulations on fire safety and construction materials for rail rapid transit systems. Fire chief, including Richardson and Casper, supported federal standards.

Local transit authorities, including Metro, opposed them. Charles Kalkhof, general superintendent of the New York City Transit Authority, said "We do not believe the establishment of another set of minimal safety standards by a federal or state body would aid us in our quest for improved safety . . ." Kalkhof and others cited the administrative burden that federal regulation would bring to the already financially pressed public transit business.