The hearing, called by the Northern Virginia office of the Virginia Air Pollution Control Board, promised to be controversial. In his opening statement, regional director Daniel J. Gaston warned that any debate would be "out of order" and not be part of the record.

A developer was seeking a permit from the board to construct a regional shopping center at the corner of Rts. 50 and I-66 just west of Fairfax City.Residents of the area, had already protested at rezoning hearings that the 39,000 auto trips that the shopping center would generate daily in an already heavily traveled corridor would produce excessive levels of carbon monoxide.

"Is there anyone who has a presentation to make" Gaston asked the audience.

The spokesmen for the shopping center developer, Fairfax Associates, said no, that the group would stand by its application.

The same answer was given by another applicant, Mobil Corp. The New York-based oil firm wants a permit to build large office building - and possible future corporate headquarters - at Rte. 50 and Gallows Road, one of the most congested intersections in Fairfax County.

"Is there anyone else who has a presentation to make" Gaston asked, anticipating some opposition.

There was no answer.

"The silence is deafening," Gaston said. "I consider the hearing closed."

As puzzled as Gaston was Geoffrey J. Vitt, the attorney who has represented Lifeline 50 Coalition, the group of residents opposing the shopping center.

Vitt said he did not attend the hearing because "I'm not taking an active role" in the coalition's efforts. But he also said, "Frankly, it had been my understanding that the citizens were going to represent themselves . . . I'm a little surprised that didn't show up. It's a mystery to me."

According to John C. Doherty, an engineer with the regional office of the Air Pollution Control Board although the shopping center would generate 39,000 vehicle trips daily, carbon monoxide levels would actually decrease in the Rts. 50-I-66 area. That would happen, he said, because of $3 1/2 million wirth of traffic-circulation improvements to be provided by the developer and because of cleaner-burning car engines mandated by the federal government.

Doherty also said the Mobil building would not result in any carbon-monoxide levels above U.S. limits at any nearby sensitive areas, such as the Fairfax Hospital emergency room. The reason, again, was improved traffic circulation and cleaner.

New construction must get a permit from the state Air Pollution Control Board if the project would generate 750 or more car trips per hour or more vehicles in eight hours. Gaston said the state would not issue a permit if the carbon-monoxide count would exceed federal standards.

Gaston said carbon monoxide, while potentially lethal in high doses, quickly dissipates, unlike another auto emission.