Radon Testing That Tells You the Truth About Your House
A radon test is cheap, takes two days, and answers a question no one can eyeball: how much radioactive gas is in the air your family breathes downstairs. We run licensed measurements across the North Shore, and we'll tell you honestly when a free county kit is all you need.
Three ways to measure
Short-term test (2 to 7 days). The standard first look and the workhorse of radon measurement. The house stays under closed-house conditions, the device sits in the lowest lived-in level, and you get a number you can act on.
Long-term test (91+ days). Radon levels swing with weather, season, and how the house is used. A long-term test averages across those swings and gives the best picture of true year-round exposure. If a short-term result lands near the action level, this is often the smart next step.
Continuous radon monitor (CRM). An electronic monitor logs the level hour by hour, records tamper conditions, and produces a timestamped report. This is the instrument for real estate deals, where 48 hours is all the inspection window allows and both sides need a result they can trust. Details on how that works during a sale are on our real estate testing page.
Why winter readings matter most here
A heated North Shore house in January behaves like a slow chimney: warm air rises and escapes up high, and replacement air gets pulled in down low, including soil gas through every crack, joint, and sump opening in the foundation. With the windows shut for months, whatever comes in stays in. That's why radon levels typically peak in winter, and why a closed-house winter test is the gold standard for knowing what your home actually does at its worst.
Most of the housing around here predates any thought of radon. Illinois only began requiring passive radon-resistant construction in new homes in June 2013, and the vast majority of homes in Northbrook, Glenview, Wilmette, and Evanston were built decades before that. Testing is the only way to find out what six or eight decades of settling have opened up under your slab.
What happens if the number is high
Nothing dramatic, and that's the point: a high test is a solved problem. A mitigation system installs in a day, runs quietly, and gets verified with a follow-up test. What you shouldn't do is re-test over and over hoping for a lower number, or average a high result away. At or above 4.0 pCi/L, fix the house; between 2.0 and 4.0, it's worth a conversation about fixing it anyway, since no level is considered risk-free.
Two days of testing beats years of wondering.
Call (224) 362-4440Frequently asked questions
Why does the house have to stay closed up during a test?
Short-term tests measure your home the way you live in it during heating season: windows shut, doors closed except for normal coming and going. Opening the house dilutes soil gas and produces an artificially low reading. Closed-house conditions need to start 12 hours before a 48-hour test begins and hold through the whole measurement.
When is the best time of year to test?
Winter. Radon levels are usually at their highest when the house is sealed and the heating system is pulling air upward, so a winter test shows you the worst-case number you and your family actually breathe. A summer test still counts, but a low summer reading is weaker evidence than a low January one.
Are the free county test kits any good?
Yes, and we'll tell you so. The Cook County Department of Public Health offers free short-term kits to suburban residents, and a charcoal kit done correctly is a legitimate first look. Where a licensed measurement earns its fee is when the result has to hold up: real estate transactions, verification after mitigation, or a reading you plan to make a decision on.
My neighbor tested low. Does that mean I can skip it?
No. Radon is driven by the soil gas pathways under each individual foundation, and two houses on the same street routinely test on opposite sides of the action level. A neighbor's result, high or low, says nothing reliable about yours.