Northern Virginia retailers yesterday reported large increases in the sale of residential smoke detectors after a fire last Saturday killed seven persons in a McLean home.

"We're totally sold out," said James Monroe, manager of the Dart Home Centers and Hardware store in McLean. "One couple that already had one detector came in and bought another after the fire. It's strictly fear that's motivating it."

Monroe said that his entire stock of 30 smoke alarms, as well as all of his separate battery replacements, was sold two days after the fire, noting that "it normally takes more than two weeks to sell that many."

Many consumers apparently bypassed smaller hardware stores and bought out the existing stocks of detectors at Sears stores, Hechinger's, Dart stores and Montgomery Ward stores in Northern Virginia.

"We happened to have a First Alert smoke detector spokesman giving demonstrations at the store this weekend," said Tommy Glaser, a salesman at Hechinger's in Fairfax City. "It's been pretty hectic here and we've sold dozens in the past few days. Everyone was mentioning the fire."

Seven members of two families who had gathered for a wedding died of smoke inhalation early Saturday when a fire, started by a smoldering cigarette butt, swept through the 20-room home at 2014 Great Falls St. Only 36-year-old businessman Leonard Ragland survived the blaze. The residence had no smoke detectors.

Dick Bukowski, a research engineer for the National Bureau of Standards, said most of the $10 to $15 detectors -- which cost as much as $100 when they were introduced in 1965 -- are capable of detecting nearly invisible levels of smoke. He said that 98 percent of all detectors approved by Underwriters Laboratories are effective in detecting smoke.

Charles Rose, public education spokesman for Fairfax County's fire and rescue services, said the detectors are most effective when placed on ceilings where smoke first accumulates, and when kept away from kitchens, bathrooms, and other sources of normal smoke or steam.

"But the detectors aren't enough by themselves," Rose said. "You've got to have fire drills and know where alternative routes of escape are located before the emergency."

Rose said about 10,000 Americans die from fires each year, and another 300,000 suffer serious burns.