Within a minute, a match placed under a newspaper on a sofa started a fire that soon consumed the living room. Three minutes later, the intense heat and fire blew out a side window. Before five minutes had elapsed, the flames were licking the walls of the house next door and in short order melted the vinyl siding and set the underlying wood panel on fire.

At that point, firefighters doused the experiment, conducted yesterday by fire safety engineers at the National Institute of Standards and Technology in Gaithersburg.

The test was conducted to measure how fire behaves in neighborhoods of close-together houses, which are becoming more common in the Washington region and other fast-growing areas.

National building codes allow single-family houses to be built six feet apart. Virginia fire officials are seeking to make the International Residential Code -- used in Virginia, Maryland, 41 other states and the District -- at least as strong as regulations adopted recently in Virginia, which will require developers to install firewalls or build homes 10 feet apart.

For the test, NIST scientists built model sections of two houses six feet apart inside the federal agency's large, 90-by-120-foot fire test chamber. Each structure had a wood frame covered with a weather-resistant wrap and finished with vinyl siding. One was furnished with a sofa, a table, an armchair, wall paneling and carpet.

"And this is by no means the worst-case scenario," said Alexander Maranghides, manager of the laboratory. He said that the test took place under wind-free conditions and that the "buildings" had only one small window on each side and no overhangs. Firefighters were also standing by with charged hoses.

Prince William Battalion Chief L. Ray Scott said the test showed that regulations are not adequate to prevent the spread of fires from house to house. He noted that it took less than five minutes from ignition to when the second wall caught on fire. He said that in Prince William, it typically takes nine minutes after a 911 call for firefighters to arrive and begin fighting a fire.

"This was built to today's code," Scott said, pointing to the smoldering remains of the fire. "It's not adequate."

Building industry officials present said the test -- while dramatic -- did not prove anything. They said that the numbers of fires and fire deaths nationally are declining and that fires of the type in the experiment are not a public safety problem.

"It wasn't unexpected," said Matt Dobson, the code and regulatory director of the Vinyl Siding Institute, a trade group.

Scott said several fires in the region were caused by proximity. In Loudoun County in 1994, three houses -- each six feet apart -- went up in flames before the first firetruck arrived. In January, a Gainesville house fire spread quickly to the house next door, 11.4 feet away.

Scott pushed successfully for the Virginia Board of Housing to adopt the new rules, which will go into effect this year.

David D. Evans, a NIST engineer, said the detailed heat and time measurements recorded during yesterday's experiment will be used to construct computer models on how fire behaves and spreads.

A second test will be conducted next week to see if a fire barrier, such as a sheet of gypsum wallboard placed under the vinyl siding, will slow down the combustion of the second house.

Within five minutes of ignition, the fire has spread from one model house section to another model structure six feet away, and firefighters are ordered to douse the flames.Alexander Maranghides, manager of the fire laboratory at the National Institute of Standards and Technology, gives directions during a briefing before the test fire.