Radon testing in Illinois homes: why our state is high-risk and how testing works

Radon is a radioactive gas produced by uranium breaking down in soil, and it enters homes through foundation cracks, sump pits, and floor drains, then accumulates in the lowest lived-in levels. It has no smell and no color, and long-term exposure is the second leading cause of lung cancer in the United States. Illinois matters here specifically: the U.S. Environmental Protection Agency rates much of the state, including Cook County and the northwest suburbs, in its highest radon potential zone, and state surveys have found elevated levels in a large share of tested homes.

The only way to know your home's level is to test. The basic options are simple. A short-term charcoal test kit, available at hardware stores and often at a discount through county health programs, sits in the lowest lived-in room for two to seven days and is mailed to a lab; kits typically cost $15 to $40 including analysis. A licensed radon measurement professional uses calibrated monitors and follows state protocols, typically $150 to $300, and their report is what real estate transactions rely on. Digital continuous monitors cost more up front and suit homeowners who want to watch levels across seasons.

Results come back in picocuries per liter, abbreviated pCi/L. The EPA action level is 4.0 pCi/L: at or above it, the home should be fixed. Between 2.0 and 4.0, the EPA still suggests considering mitigation, and the World Health Organization's reference level is lower, at about 2.7. One important testing detail: a single short-term test is a snapshot, and levels swing with weather and season, running higher in winter when homes are sealed and the furnace creates stack effect. A result near the action level deserves a follow-up test or a long-term test that averages ninety days or more.

If the number comes back high, what does mitigation involve? The standard system is sub-slab depressurization: a pipe through the basement floor into the soil below, with a small fan that draws radon out and vents it above the roofline. Installed systems in the northwest suburbs typically run $1,200 to $2,000, the fan uses about as much electricity as a light bulb, and a manometer on the pipe shows at a glance that the system is running. In Illinois, radon mitigation contractors must be licensed by the Illinois Emergency Management Agency, so verify the license before signing; it is a quick check and legitimate firms expect it.

Radon also belongs in real estate conversations. Illinois law requires sellers to provide a radon disclosure and an informational pamphlet, and buyers commonly test during the inspection period. If you are selling a home in Barrington or Wheeling and have never tested, testing before you list removes a surprise from the negotiation. If a test comes back high, mitigation is a well-understood, fixed-price fix that rarely delays a closing when handled early.

January is national radon action month and a natural reminder, but any month works for a two-day test. Start with a kit on the lowest lived-in level, follow the closed-house instructions that come with it, and write the result in your home file. The directory's home safety pros and inspectors across the northwest suburbs can take it from there if your number comes back at or above the action level.