Arlington restaurants may be asked soon to begin voluntarily reserving no-smoking sections for their patrons under a resolution that the County Board is expected to adopt Saturday.

Although an estimated that 30 to 50 percent of the county's nearly 500 restaurants and fast food outlets already have such no-smoking sections, the board is expected to approve a resolution urging the others to follow their example.

The proposal before the board asks that restaurants with a seating capacity of 75 persons or more set aside at least 25 percent of the area for nonsmokers, according to Glen Rutherford, chief of the county's environmental health division.

Although some may want to make no-smoking sections mandatory, Assistant County Attorney Naomi Klaus said, the Virginia Supreme Court ruled that such a requirement was unconstitutional when Newport News enacted one.

"The problem was that smoke can go all over a room. There's really no way to contain it, so it's unreasonable to set up an area which doesn't solve the problem," Klaus said, explaining the court's decision.

"I'll be interested in seeing how well this works on a voluntary basis," said Mary Margaret Whipple, the County Board's vice chairman, predicting the board's approval of the resolution. "I'm anxious to protect patrons in restaurants and other public places from cigarette smoke."

Arlington already has an ordinance barring smoking in stores and other public areas where more than eight persons are present or employed, unless there is a separate, specially designated smoking area. Violators can be fined up to $25.

John S. Cockrell, executive vice president of the 1,100-member Restaurant Association of Metropolitan Washington, said his organization does not endorse mandatory no-smoking sections "because some places simply can't comply. But we do urge members to do it voluntarily."

"The industry really doesn't think the smoking is as bad as some people make it out to be because of the high velocity of air in restaurants," said Cockrell, a nonsmoker. "Every several minutes, every bit of air is changed, as required by health laws. It's not like sitting around a room at home that gets filled with smoke."

Mandatory compliance would be difficult for some restaurants, particularly the smaller ones that have no way of segregating smokers and nonsmokers, Cockrell said.

Sergio Micheli, owner of the Firenze and Portofino restaurants in Arlington, agreed. "I don't know how they expect owners to police that," said Micheli, who plans to comply with the requested no-smoking areas in his multiroom restaurants. "If you have more than one room, you can designate a room for smoking and no-smoking. But otherwise, what do you do? Set aside a corner of a room?"

The County Board's no-smoking resolution is being raised in connection with a proposed overhaul of local laws applying to food establishments. The changes would bring the county code up to federal and state standards.