In a building that once housed the McLean Volunteer Fire Department, 300 Fairfax teenagers, parents and community leaders celebrated the opening Saturday of the only publicly funded teen center in Northern Virginia.

"It's exhilarating. People in the community are just really energized," said Cheryl Bell, chairman of the board of the McLean Community Center, which is responsible for the funding of the teen center.

Under the terms of a two-year lease set by the Fairfax County Board of Supervisors, the Old Firehouse Teen Center, located in downtown McLean, will be open to all teenagers living in Fairfax County for a membership fee of $10.

Equipped with a television and a VCR, a sound system, pool tables, an air hockey table, a jukebox and a variety of pinball and video machines, the center was paid for with funds raised by the community.

The McLean Community Center Governing Board allocated $250,000 for the renovation, which kept intact much of the original building. The center's annual budget will be $150,000, according to Page Shelp, executive director of the community center.

When the supervisors first made public plans to turn the old firehouse into a place for Fairfax teens to gather, local architect Al Pierce volunteered his services.

"We thought there was a very strong need for a place for kids to go in McLean," said Pierce. "There really isn't anywhere else for them to gather after school in a safe environment."

The teen center's newly appointed manager, Alexandra Mattson, said the security of the teens will be a priority at the center. The center will be drug- and alcohol-free, Mattson said, and there will be two adults on duty at all times.

On opening day, parents were being recruited as supervisors. The center hopes to attract 25 to 30 teens daily and has the capacity to handle 250 for special events such as dances that will be held on Friday and Saturday nights.

Before beginning his design work in the summer of 1989, Pierce consulted with the McLean Community Center Teen Council. "We had an all-day programming session where we discussed their views on what the center should be like. They really drove home that they were afraid that separate spaces would cause the kids to go off into groups and not mingle."

A teen council will participate in running the center. Arlie Fischer, a 12th-grader at McLean High and co-chairman of the teen council, said that the center's first priority is to boost its membership.

The two-year lease is conditional upon the membership reaching 1,500 high schoolers and 500 junior high youths. If that goal is not met, "the lease will be canceled," said Fischer, "and they'll turn it into a parking lot."

In its first three hours of operation Saturday, the center recruited 120 members, but the vast majority were in junior high school, a fact that had Vanna Orbona, an 11th-grader at Langley High, slightly worried. "No offense to junior high kids," said Orbona, "but if we get a lot of them, the high school kids might not want to come."

The center had decided to separate the high school teens from those in junior high, and to limit the times that junior high youths can use the center to alternate Saturdays. But in the face of the initial membership figures, "our decision may have to be altered," Mattson said.