The General Services Administration yesterday proposed an almost total ban on smoking in the 6,800 buildings it owns or leases. The proposal would affect about half of the government's 2.8 million civilian workers, and most of the 350,000 employes here.

Because the federal government is the nation's largest employer, the action could trigger similar bans in private firms.

Under the plan -- scheduled to take effect in the fall -- cigarette, pipe and cigar smoking would be banned in general office space, lobbies, hallways, restrooms, elevators, libraries and classrooms. Smoking would be allowed in private offices, but agency heads -- who would be allowed to toughen the GSA rules but not weaken them -- could ban smoking in individual offices.

The only smoking areas provided for in the regulations would be special areas of cafeterias and around vending machines or canteen areas.

The ban would not apply to most buildings used by the Defense Department and the U.S. Postal Service because they are not GSA-owned or -leased. However, the rules would apply at the Pentagon, which has 23,000 civilian and military personnel, because it is a GSA-controlled building.

A Defense Department spokesman said the armed services are already engaged in a vigorous campaign to discourage smoking, segregate smokers and limit smoking to specific areas.

GSA's proposed regulations were published in the Federal Register yesterday and announced by GSA Administrator Terence C. Golden, who was attending a fitness and health conference in Seattle. Golden, 41, is a runner and frequent competitor in amateur races. He is also "death on smoking," according to subordinates at the agency, which acts as the government's landlord and housekeeper.

Golden said the smoking ban is part of a "total wellness" program that includes improving the work environment in federal agencies and encourages them to set up exercise facilities. Golden said the effects of smoking are responsible for 340,000 deaths each year and that "cigarette smoking is the chief avoidable cause of death in our society."

Unions representing federal workers generally praised the GSA proposal.

Robert Tobias, president of the National Treasury Employees Union, said his union is "very concerned that employes have a healthy place to work, and if that means banning smoking in some areas, we support it."

Kenneth T. Blaylock, president of the American Federation of Government Employees, said his union recognizes the health hazards of smoking, but "we question the need for centralized regulations that narrow the scope of bargaining." He said agencies and federal unions should negotiate a policy that is fair to smokers and nonsmokers alike.

Under the federal rule-making procedure, each government agency will have 60 days to comment on the GSA proposal. Once those comments are received and studied, GSA will issue final regulations that would go into effect immediately.

Although many federal agencies have taken steps to curb smoking, policies vary. The Merit Systems Protection Board and one section of the National Institutes of Health have banned it. In some agencies, workers have voted on an office-by-office basis to ban smoking, but most agencies allow it in private offices, parts of cafeterias, lobbies and some restrooms.

Golden, a former Treasury Department official who has headed GSA for 10 months, said scientific evidence points to a danger to nonsmokers who must work with smokers, adding that the regulations will permit smoking "provided such action does not cause discomfort or unreasonsable annoyance to nonsmokers . . . . "

GSA officials said yesterday's proposal does not carry penalties for workers who defy the smoking ban. "We would expect those will be developed when we receive agency comments," a spokesman said.