Why a Radon Real Estate Test Matters in Metro East Illinois Home Sales

When you are selling or buying a home in the Metro East area, especially around Belleville, Edwardsville, O'Fallon, or Collinsville, the conversation often turns to the home inspection. Most people expect the inspector to check the roof, the foundation, and the HVAC system. But there is another hazard that does not get the same attention, yet it can be just as important to the deal. I am talking about radon gas. This invisible, odorless radioactive gas seeps up from the soil and can accumulate inside a house. If you are involved in a real estate transaction, understanding what a radon real estate test involves and why it matters can save you from surprises later.

The Science Behind the Concern

Radon gas forms naturally when uranium in the ground breaks down. It moves through the soil and can enter a home through cracks in the foundation, gaps around pipes, or even through the water supply. The EPA has set a recommended action level of 4 picocuries per liter of air. Above that level, the agency advises you to install a radon mitigation system. In Illinois, especially in areas with certain soil types, elevated radon levels are not uncommon. I have seen homes in O'Fallon that tested below 2 pCi/L and others in the same neighborhood that hit 8 or 10 pCi/L. The variation depends on the home's construction, the soil, and the weather on testing day.

The real point here is that you cannot guess. You need a proper test. This is where the radon real estate test comes into play. It is a specific type of measurement designed to give you a snapshot of the radon level during the period of a real estate transaction. The test usually lasts between 48 hours and 90 days, depending on whether you choose a short-term radon test or a long-term radon test. For a real estate deal, the short-term test is almost always the choice because time is tight.

Short-Term vs. Long-Term Testing

A short-term radon test typically uses an activated carbon device. You open the package, set it in the lowest livable area of the house, leave it for two to seven days, and then mail it to a lab. The carbon absorbs radon, and the lab measures the radioactivity. It is cheap and fast. But it can be influenced by weather, open windows, or even how often the HVAC runs. A long-term radon test, on the other hand, uses an alpha track detector. It sits in the home for 90 days or more and gives a more accurate annual average. That is great for homeowners who want to know their year-round exposure, but it is too slow for a real estate transaction.

There is also the continuous radon monitor, which plugs into a wall and gives hourly readings. Some home inspectors use these for a radon real estate test because they can detect tampering or unusual spikes. But they cost more, and the seller may not want to wait for a full 48-hour run. The choice depends on the situation. In my experience, the activated carbon test is the most common for home sales. It is reliable enough when done correctly, and the price is right.

What Happens When the Test Shows High Levels

If the test comes back above 4 pCi/L, you have some decisions to make. The buyer can ask for a radon mitigation system to be installed. The seller can negotiate on price or offer a credit. Or the seller can install the system before closing. The most common type of mitigation is a sub-slab depressurization system, also called active soil depressurization. A contractor drills a hole through the basement floor or slab, pulls a vacuum on the soil below, and vents the radon gas above the roofline using a radon fan. The fan runs continuously, and a manometer on the pipe shows whether it is working. If the manometer reads negative pressure, the system is pulling gas from under the house and sending it outside.

Companies like RadonAway make most of the fans you will see around here. Air Sense Environmental handles testing and mitigation for many homes in Belleville and the surrounding areas. They can install a system in a day or two and then do a follow-up test to confirm the levels have dropped. I have seen levels go from 12 pCi/L down to 1.5 pCi/L after a proper system goes in. It is not a huge expense compared to the health risks. And for a buyer, knowing the home has a working mitigation system can be a selling point.

Common Mistakes in Real Estate Radon Testing

I have seen a lot of things go wrong with a radon real estate test. The most common mistake is closing windows and doors too late. The test requires closed-house conditions for at least 12 hours before the test starts and for the entire test period. That means no opening windows, no running window fans, and minimal use of the HVAC system's fresh air intake. If someone opens a window for five minutes during the test, the results can be artificially low. That helps no one, especially the buyer who moves in and then gets a higher reading during the first year.

Another mistake is placing the test device in the wrong spot. It needs to be in the lowest livable area of the home, at least 20 inches above the floor, away from drafts, heat sources, and exterior walls. A laundry room with a dryer running can mess up the readings. A basement workshop with a chemical smell can also cause problems. The best spot is a seldom-used bedroom or a living area in the basement.

I also see people confuse a home inspection with a radon test. They are not the same thing. A home inspector may offer radon testing as an add-on service, but the equipment and the protocol are different. The radon test is a separate measurement that requires specific handling. Some buyers skip the test entirely to save a hundred dollars, then later find out the hard way that the house has a radon problem. That is false economy.

Timing and Logistics in a Transaction

Timing is everything in a real estate transaction. The radon real estate test usually happens during the inspection period, which might be 10 to 14 days after the offer is accepted. The seller needs to agree to keep the house closed, and the buyer's agent needs to coordinate with the testing company. If the test gets delayed, the inspection period can expire, and the buyer loses the right to negotiate. I have seen deals fall apart because the test was not started early enough. The buyer ended up buying a home with high radon and no recourse. That is why I recommend scheduling the test as soon as the offer is accepted, even before the general home inspection if possible.

In Metro East Illinois, the weather can also affect the test. Winter tests tend to show higher radon levels because the house is sealed tight and the stack effect pulls more soil gas inside. Summer tests can be lower if the home has open windows. But you cannot control the season. You can only follow the protocol and get the results. If the test comes back borderline, say 3.5 or 4.0 pCi/L, you might consider a long-term test or a continuous monitor to get a better picture. But in a transaction, time usually does not allow that. You take the short-term test as a baseline and move forward.

Mitigation Systems and Ongoing Maintenance

If a radon mitigation system is installed, it is not a set-it-and-forget-it solution. The radon fan needs to run continuously. The manometer should be checked periodically to make sure the system is still pulling suction. If the manometer shows zero or a positive reading, something is wrong. The fan may have failed, the pipe may be blocked, or the seal around the slab may have broken. I have seen homeowners turn off the fan to save electricity, not realizing that the radon levels can climb back up within days. A system that is off is no system at all.

Maintenance is simple. Look at the manometer once a month. Listen for the hum of the fan. If the fan is quiet, it might be running fine. But some fans are so quiet you cannot tell. That is why the manometer is the best indicator. If the fluid levels are different between the two legs, the system is working. If they are equal, the system is not pulling vacuum. Call a professional like Air Sense Environmental to check it out.

Wrapping Up

Radon is not a topic that comes up at every dinner party, but it should be part of every home sale conversation in this region. The radon real estate test is a simple, affordable tool that gives both the buyer and the seller peace of mind. It is not about fear. It is about knowledge. When you know the level, you can make a decision. You can negotiate, install a system, or walk away. Without the test, you are buying or selling a home with a blind spot. In the Metro East area, where radon levels can vary block by block, that blind spot is just not worth the risk.

If you are a seller, consider doing a radon test before you list the house. That way, you can address any issues ahead of time and present a clean report to potential buyers. If you are a buyer, insist on the radon real estate test as part of your inspection. It is a small price for a big piece of information. And if you are an agent, make sure your clients understand what the test involves and why it matters. A smooth transaction depends on everyone being on the same page, and radon testing is one page you do not want to skip.