Using their peculiar methods -- gun-toting security guards at the Pentagon, overseas cables at the State Department, open forums at the Environmental Protection Agency -- federal agencies are falling into line behind new regulations limiting smoking in government buildings, issued last December by the General Services Administration.

One common impression emerged from reports of 18 government agencies yesterday at a meeting of the Interagency Committee on Smoking and Health, chaired by a stern-faced surgeon general, Dr. C. Everett Koop: The last bastion for federal employes who smoke is likely to be a federal restroom.

Otherwise, the morning offered occasionally hilarious glimpses of each agency being true to the rules in its own fashion.

For example, EPA officials decided that because one-third of its employes smoked, smoking would be allowed in restrooms on every third floor of the high-rise towers at EPA headquarters. The policy means that "employes don't have to travel more than one floor up or down to get to the restroom of their choice," explained John Chamberlin, director of the agency's Office of Administration.

"We got plenty of emotional responses and grumbling," Chamberlin said. "There was no consensus at all either for or against the policy." Echoing the experience at other agencies, Chamberlin said opposition to the new restrictions has died down since they were imposed at the EPA last June.

At the Department of Defense, smoking is restricted to certain office areas, cafeterias and snack bars, and some restrooms with separate ventilation systems, said Michael J. Langone, director of safety and occupational health at the department's Washington Headquarters Service.

At first, nonsmokers unhappy with the choice of restrooms stole or defaced many of the "designated smoking area" signs, Langone said, forcing the department to buy signs that could be screwed down.

Langone said department officials decided "to employ the services of the federal protection officers" to enforce the new policy. He reasoned that a visitor who entered a Defense building with a cigarette and who was stopped by a gun-carrying guard "might say, 'He means business.' "

At the State Department, smoking is allowed only in private offices and in designated areas of cafeterias, according to Stephen Urmen, director of safety. In the spirit of diplomacy, employes are instructed to report violators to superiors rather than confronting them, which might lead to "verbal abuse," Urmen said. He added that the department's overseas posts have been directed to develop similar policies, "which also allow for cultural norms at each post."

Dr. Otis R. Bowen, secretary of Health and Human Services, announced in May that smoking would be banned in all HHS buildings beginning Aug. 25. But the ban is not in force everywhere, according to James A. Johnson, acting director of HHS's Office of Special Program Coordination. He said some buildings have had restrooms with separate ventilation systems designated as smoking areas to allow employes who smoke a six-month grace period.

HHS officials have also determined that, when negotiated agreements with unions are at variance with the smoking ban, they must be allowed to expire before the ban takes effect, Johnson said.

At the close of the session, Koop presented a golden medallion on a striped ribbon to GSA Administrator Terence C. Golden, who championed the regulations against strong opposition from tobacco lobbyists, for "outstanding contributions to nonsmoking and health."

Looking like the quintessential gray-suited bureaucrat, Golden stood as Koop put the ribbon around his neck. Then he rushed back to his seat and took it off.