Fairfax County residents who pick up a playboy, Gallery, or Playgirl magazine along a loaf of bread or a bottle of aspirin at their local variety store may have to make a special resquest for those magazines in the future, if County Board Chairman John F. Herritty has his way.

Herritty said yesterday he will ask his fellow supervisors to pass an emergency ordinance aimed at banning the display of all such magazines. The law would ban display of material "harmful to juveniles."

A current county ordinance prohibits the sale of obscene publications and films to abyone, but does not address materials that may be "harmful to juveniles."

The proposed legislation would incorporate the current Virginia state prohibition against the sale or loan to anyone under 18 of materials that are "harmful to jufeniles" and would also "go a bit further in covering the display (of such materials)," according to Assistant County Attorney James P. Downey, who drafted the new county ordinance.

Downey conceded that determining what is "harmful to juveniles" is "obviously going to be a problem." In the draft legislation this is defined as any description or representation that "predominantly appeals to the prurient, shameful or morbid interests (or) is patently offensive to prevailing standards in the adult community as a whole with respect to what is suitable material for juveniles."

Most stores that carry the magazines in Fairfax now display them in deep racks that hide the magazine covers except for the titles. But the magazines are still accessible for viewing to persons under 18 years of age, and that is the reason for the proposed ordinance.

"This type of filth and pornographic material should not be available to the teen-agers of the country," Herrity said yesterday. "The practical effect of the new ordinance will be to put (the magazines) under the counter," he said.

Patricia Hoskins, a Drug Fair store manager, reported yesterday that 14 or 15-year-old occasionally look at such magazines on display but that "it is not a big problem: it's not a steady thing - at least we've not caught them at it." Several other store employees in Fairfax yesterday repeated Hoskins' observation.

Spokesmen for Dart Drug and 7-Eleven Stores said yesterday they would abide by any ordinance the supervisors might enact. But the 7-Eleven official conceded that "it would hurt us" because keeping the magazines out of sight cuts down on "impulse sales."

The Fairfax 7-Eleven stores did keep such magazines under the counter for about three or four months within the past year because of some customer complaints, but the practice was stopped because sales went down, a spokesman said.

Most of the supervisors queried yesterday said they would vote for the proposed ordinance when Herrity requests action on it in two weeks, although a couple of supervisors expressed concern about the ordinance's constitutionality and "practicality."

Martha V. Pennino (D-Centreville) said she would vote for banning the display of such magazines because she saw "no redeeming value to society" in them.

Downey said he knew of no other jurisdiction in the metropolitan area that has banned the display of materials "harmful to juveniles."