Nonsmoking federal workers have won another important round in their fight to make their offices free of tobacco smoke. The new ruling, from the General Accounting Office, could encourage some federal officials to crack down on smoking in buildings owned or rented by the government.

In a just-released decision dated Aug. 22, the GAO says that government agencies have the authority to purchase desktop air purifiers to filter cigarette smoke. Earlier GAO rulings on the subject had generally limited agencies to buying air purifiers only for work spaces that were open to the public.

The decision (B-216856) says the government can't pay the medical expenses for employes trying to kick the smoking habit, but it reminds agency heads that they already have the legal authority to restrict smoking to certain areas of their buildings and, in some cases, to ban it. Most federal agencies have no-smoking areas in conference rooms and cafeterias but few have banned smoking altogether.

GAO's decision was prompted by an Interior Department query about the purchase of air filters, payment for "rehabilitation" programs that help smokers kick the habit and the overall government policy on smoking in federal buildings.

GAO said the government may pay for air purifiers for instances in which there would be a "generalized benefit to all employes working in the area."

The congressional agency said that federal agencies may encourage programs that help employes to stop smoking, but cannot pay for personal medical expenses "incurred as a result of their participation in a smokers' rehabilitation program . . . . "

As to banning smoking in federal buildings, GAO said that current federal regulations "do not anticipate a total prohibition against smoking" but that "under certain circumstances an agency has the authority to ban smoking within the space allotted it. For example, General Services Administration regulations state that local laws be complied with wherever applicable and employes may unanimously declare an office a no-smoking area.