By James Heffernan — Daily Staff Writer

WINCHESTER — A silent killer may be slipping through the cracks and into your home. Once inside, it gets into the air you breathe and begins its assault on your respiratory system.

Radon, an invisible, odorless gas that forms from the natural breakdown of uranium in soil, rock and water, is the second-leading cause of lung cancer in the U.S. behind smoking, accounting for about 21,000 deaths per year, according to the Environmental Protection Agency.

The radioactive gas can get into any type of building, but people are most likely to be exposed to it in their home, where they spend most of their time. Radon typically moves up through the ground to the air above and into your home through cracks in the foundation, gaps around service pipes and under suspended floors.

The EPA estimates that one out of every 15 homes in the U.S. has elevated radon levels.

However, Gerre Pittenger, owner of Tri-State Radon Specialists in Winchester, puts the local figure as high as one in three, in part because Virginia is one of the richest states in the nation in uranium.

"It's very common," said Pittenger, whose company has been monitoring indoor radon levels and installing home mitigation systems for more than a decade. "It doesn't matter whether your home is old or new. The only way to tell about radon is to test for it."

Pittenger said he has tested entire subdivisions in Winchester and found that 80 percent of the homes had radon levels far above what the EPA considers safe — generally 4 picocuries per liter or higher.

The average indoor radon level is estimated to be about 1.3 pCi/L, according to the EPA. With the proper measures, most homes can be reduced to 2 pCi/L or below.

Indoor radon levels tend to be highest in the winter, when homes are shut up and there is a temperature differential of more than 30 degrees between the inside and outside air, creating what is known as a "stack effect," Pittenger said.

"Your home acts like a vacuum," he said. "It's actually sucking in air from the ground. ... It's worse when the wind is blowing."

Testing your home is the only way to determine if it has elevated levels of radon, the EPA says.

There are many kinds of low-cost, do-it-yourself radon test kits available in hardware stores and other retail outlets, and some states, like West Virginia, distribute them to homeowners free of charge through the mail.

The most simple radon test involves putting an activated charcoal filter canister in the basement for three to seven days and then returning it to a laboratory for analysis. The "alpha-track" sampler test method involves leaving the device in the home for a longer period, from 30 days up to one year, before it is returned to a laboratory for analysis. Other testing methods include "continuous monitors" that provide results within 24 to 48 hours.

The EPA suggests that you first conduct a short-term test — from two to 90 days, depending on the kit — and if the level is close to 4 pCi/L, follow up with a long-term test to determine if you need a mitigation system.

If mitigation is required, Pittenger said his company drills a 5-inch hole in the basement slab to get to the gravel layer, then runs a ventilation system directly up to the roof line and outside.

"You're removing the radon before it enters the house," he said.

Radon testing is becoming increasingly common during real estate transactions.

The Virginia Association of Realtors lists radon as "an issue of concern" but not one of panic.

Radon is a "fixable problem," the group says. If an elevated level is confirmed, steps should be taken to reduce it. Because fixing a home often requires special knowledge, skills and tools, repairs are usually done by a certified radon mitigator.

Pittenger said some sellers are surprised when a prospective buyer wants a radon test done.

"It's generally younger people or families with young children [who request it]," he said, as children tend to be more susceptible to radon because of their smaller lungs.

Pittenger said a home mitigation system can cost anywhere from $700 to $2,000, depending on the radon level and the labor involved in reducing it.

*Contact James Heffernan at jheffernan@nvdaily.com