Robert Mitchell doubts he would have gotten around to testing his basement accounting office for radon if Ted Brown from his community association had not offered to help do it.

"Individually, I probably would not have" tested, said Mitchell, who lives in the Lake Vale Court neighborhood, a collection of 49 brick and colonial homes near Vienna. "But the fact is, Ted made it quite attractive and easy."

Brown is helping 26 of his neighbors test their homes for radon, a colorless, odorless, radioactive gas produced by the natural breakdown of uranium in the soil.

Brown's Lake Vale Association is one of a handful of civic groups in Fairfax County helping residents test their homes for the gas, which the EPA estimates causes 5,000 to 20,000 lung cancer deaths in the United States each year.

Brown first brought up testing at an association meeting two years ago.

"Radon is one of the things that can go wrong. (Testing) is just an ounce of prevention," he said. "We thought we should probably do something on our own if the county wasn't doing anything."

The association sent out an announcement in its newsletter offering to order home radon detectors at $22 apiece from a California manufacturer if the homeowner paid for them. At first, only about 10 homeowners signed up.

"Some of them didn't really want to know. They said, 'My God, my kids grew up here.' They were quite apprehensive about it," Brown said. Some believed "they have to die of something. If it's radon, it's radon," he said.

But increased media attention and more letters convinced more homeowners to participate, he said.

He is testing 17 houses this winter, he said.

He drops off and installs the kits at the houses, and picks them up after two or three months when they are ready to be sent to a laboratory for analysis.

In 1986, the Fairfax County health department began a two-year survey of 2,400 county homes to get an idea of radon levels in the county.

But, said project director Steven Church, "this is a study, not a service," and most homeowners must arrange to test their houses themselves.

Radon radiation levels are measured in picocuries per liter. The EPA suggests taking corrective action at levels above four picocuries, a level that reflects a health risk equivalent to smoking eight to 10 cigarettes a day.

At levels above 20 picocuries, or a risk equivalent to smoking almost two packs a day, the EPA recommends immediate action.

Indoor radon levels usually are tested in winter, when the levels are higher than those found in the summer, when ventilation is better.

The county's preliminary report found that about 32 percent of the 1,030 homes tested had levels above four picocuries, with 2 percent above 20 picocuries.

Generally, Church said, homes in the northwestern parts of the county had the highest levels.

Many homes had very little radon radiation, but one had a level of 202 picocuries.

Brown's tests also have found a wide range in radon levels in homes.

Brown said about half the houses he has tested had levels near or above four picocuries, and one house basement had a reading of 28 picocuries.

Home radon tests still are not widely available in stores. Safeway stores and WJLA-TV (Channel 7) have launched a campaign to sell 50,000 detectors, but at least in Fairfax County, shipments at supermarkets sold out within hours of being delivered Saturday.

Two of the most popular types of tests may be ordered by mail.

Charcoal absorption tests cost between $10 and $25, according to the EPA, and should be left hanging in a basement or other low-lying room for three to seven days before being sent to a laboratory for analysis.

Alpha-track detection kits, which are what Brown uses, cost $20 to $60, and may be left in a house for three months to a year. They may produce more accurate results than the charcoal tests.

If high levels of radon are found, it may be reduced by sealing cracks in basement floors, sump pump holes, dirt floors and other areas through which radon may enter a house, or by ventilating a basement.

Such work can cost from a few hundred dollars or less up to about $2,000, depending on the type of work needed, health officials said.

The Virginia Department of Radiological Health provides a list of companies offering radon test kits and contractors performing radon reduction work.

The list and other information about radon may be obtained in Virginia by calling (800) 468-0138 toll-free. The Fairfax County health department offers similar assistance at 246-2300.