J. Lynn Helms, head of the Federal Aviation Administration, promised yesterday that his agency would propose regulations within a month requiring airplane seats to be fire-retardant.

In testimony before the House Science and Technology subcommittee on transportation, aviation and materials, Helms said the FAA has gathered enough test data to justify requiring seat fabrics to contain a fire-blocking layer that would delay their ignition. Currently, the FAA has only very minimal regulations regarding the flammability of interior materials on airplanes.

Helms' announcement comes after an in-flight fire swept through an Air Canada DC9 on June 2, killing 23 people. But Helms said that the agency had been moving to issue the regulations long before the incident.

The regulations will deal only with seat materials, not wall or ceiling panels or carpeting. Helms said it would take at least another year of research before standards could be issued for fireproofing those materials.

Helms said, however, that "seats are by far the most important element in spreading aircraft fires."

Under the forthcoming rules, airlines would be required to retrofit their aircraft with the new fire-retardant fabrics. Airlines normally replace the seat covers every three years, and it was unclear whether they would have to make the change more quickly or whether they would be allowed to replace the fabrics when the old seats wore out.

Subcommittee Chairman Dan Glickman (D-Kan.) said that the current standards, issued in 1974, "provide no useful protection to passengers. . . . There virtually are no standards . . . . The assumption has been, if a plane goes down, it's too late for the people inside." He said his committee is trying to prove otherwise.

Cabin materials must now pass a test in which fabrics and cabin panels are held over a small, open flame in a laboratory. The materials must meet certain standards for burning speed and for extinguishing when removed from the flame, which is similar to a Bunsen burner.

Both Congress and the National Transportation Safety Board have been pushing the FAA for years to tighten fire standards for cabin interiors.

Glickman said that Helms had promised at a hearing a year ago to issue regulations, and a staffer for the House aviation subcommittee said the FAA, then under administrator Langhorne Bond, had promised at hearings in both 1979 and 1980 to issue regulations on fire-retardant standards within a year.

FAA spokesman Ed Pinto said the new regulations are being issued "on schedule."

The proposed regulations, which will require the standard comment period before being issued in final form, will not deal with what many aviation safety experts consider the more critical problem in fires: smoke and toxic fumes.

Standards and regulations for that may be years down the road, according to FAA spokesman Fred Farrar. "It's a very complex subject," he said. "It's very easy to burn something in the laboratory, but we have to deal with what is in the real world."

NTSB spokesman Rachel Halterman called Helms' announcement "an important step."

She said, however, that while the FAA may have been on schedule, "They are on the schedule they set, and the question is how long it took the FAA to do research, to put some emphasis on cabin fire safety."