Radon is one of those home hazards that gives you very little to work with. You cannot see it, smell it or hear it. There is no stain on the wall or strange noise in the attic that tells you it is present. The only practical way to know the level inside a home is to test for it.

For St. Louis homeowners, that makes radon testing less about chasing a symptom and more about getting a reliable measurement. The result gives you information you can use to decide whether additional testing or mitigation should be considered.

What a radon test actually measures

Radon is a naturally occurring radioactive gas that can enter buildings from the soil. A radon test measures the concentration of that gas in indoor air, usually in picocuries per liter, written as pCi/L.

The U.S. Environmental Protection Agency recommends taking action to reduce radon when a home tests at 4 pCi/L or higher. EPA also advises homeowners to consider action when results fall between 2 and 4 pCi/L.

That number is not a pass-or-fail grade in the way people sometimes imagine it. It is a measurement used to guide the next decision.

When St. Louis homeowners should consider testing

A radon test makes sense if a home has never been tested, if you are buying or selling, or if major changes have been made to the foundation, ventilation or lower-level living space.

It can also be worth retesting after a mitigation system has been installed or after significant renovation work. Changes to the building can affect air movement, which is one reason a result from many years ago does not always answer the question forever.

Homes next door to each other can produce different results, so a low reading at a neighbor’s property does not tell you what is happening in yours.

Why a radon map cannot replace a test

EPA publishes radon-zone maps, but the agency specifically warns against using those maps to decide whether an individual home needs testing. The maps were designed to help governments and organizations plan resources, not to predict the result in one basement.

That distinction is important. You do not need to prove that your neighborhood is a high-radon area before testing. The test itself is what answers the question for your home.

Short-term and long-term testing

Different test periods provide different kinds of information. Short-term testing can provide a faster snapshot when timing matters, such as during a real-estate transaction. Longer-term testing can give a broader picture of average exposure over time.

Whichever method is used, placement and test conditions matter. A device should be positioned according to the instructions for the test rather than moved around the house based on convenience.

For a real-estate transaction, follow the protocol required for that test and confirm whether a particular report or procedure is expected by the parties involved.

What happens if the result is 4 pCi/L or higher

If the result meets or exceeds EPA’s 4 pCi/L action level, the next step is to discuss mitigation with a qualified radon professional. A mitigation system is designed to reduce the amount of radon entering or accumulating inside the home.

Around The Clock Pest Control provides professional radon testing in Greater St. Louis. Testing and mitigation are separate decisions. First you need an accurate result; then you can decide what action makes sense based on that result.

Why proper testing conditions matter

Indoor radon levels can vary with weather, ventilation, foundation conditions and the way the home is operated. Opening windows, moving the device or ignoring test instructions can affect the usefulness of the reading.

A properly conducted test gives you something far more valuable than a guess: a documented measurement from the home itself.

Frequently asked questions

Can you smell radon?
No. Radon is invisible and odorless, which is why testing is necessary.

Is 4 pCi/L a legal limit?
EPA uses 4 pCi/L as an action level in its public-health guidance. Local or transaction-specific requirements may differ.

Should I test if my neighbor had a low result?
Yes. Radon levels can vary from one home to the next, even on the same street.

For radon testing in St. Louis, call (314) 303-7240 or request service.

Authoritative reference: U.S. Environmental Protection Agency guidance on radon testing and the EPA Map of Radon Zones.