Radon is a household concern that often goes unnoticed, even in homes that appear perfectly safe. This naturally occurring radioactive gas is present in approximately one in every 15 homes across the U.S.
What makes radon particularly concerning is that it doesn’t come from manmade pollution like factory emissions or industrial accidents. Instead, it forms deep underground through the natural decay of uranium, a mineral found in almost all soil and rock.
As uranium breaks down, it produces radon gas. Outdoors, that gas disperses harmlessly into the atmosphere. However, inside a home, where air becomes trapped and recirculates, radon can collect and reach concentrations that pose serious long-term health risks. That means what produces radon in homes originates entirely from the natural geology beneath your foundation.
In this article, we’ll break down where radon comes from in homes and how it moves from the soil into your living space. You’ll learn the subtle pathways a house can develop over time, how air pressure inside your home can pull radon upward and why testing is the only reliable way to know if you’re at risk.
Can You See or Smell Radon?
No — the problem with radon is that you won’t typically notice when it’s present. You might expect a strange smell, visible dust or some type of stain or residue, but radon doesn’t leave clues behind. It’s completely undetectable by human senses — you can’t see, smell or taste it.
There are no general signs of radon in your house, such as discoloration on walls, odd odors or changes in air quality that you can feel. And unlike carbon monoxide, radon exposure doesn’t produce immediate symptoms. Health problems, such as increased lung cancer risk, develop only after long-term exposure to elevated radon levels.
Since this radioactive gas is undetectable, testing is the only way to know whether it’s in your home.
Common Entry Points in Your Home
Radon enters a home by slipping through small openings, structural gaps and natural pathways — so quietly that most homeowners never realize it’s happening.
Here’s how radon gets in your house:
- Cracks in the foundation: Even tiny hairline fractures in concrete slabs or basement floors can allow radon gas to flow freely from the soil into your living space.
- Gaps around pipes and wires: Openings made for plumbing lines or electrical cables often leave unsealed spaces that create a direct channel for radon to enter.
- Construction joints: Where walls meet floors, or where different sections of a foundation connect, subtle gaps can form over time. These joints act as natural pathways for radon.
- Unsealed sump pumps and drains: Sump pits, floor drains and similar features often sit in direct contact with the soil. If they’re not properly sealed, they can become major entry points.
- Cavities inside walls: Voids between walls can draw radon upward from the soil and distribute it throughout the home via air movement and pressure changes.
Since radon is a gas, it only needs the smallest gap to push through, which is why checking your levels is so important. Whether it’s a brand-new construction or decades old, insulated or drafty, any type of home can create conditions that allow radon to enter.
The “Stack Effect” — How Your Home Pulls Radon Inside
If openings in the foundation are the doorway for radon gas, the stack effect is the force pulling it in. Here’s a simple breakdown:
- Warm air inside your home rises.
- When that warm air escapes through the upper levels — attics, roof vents, upstairs windows — it creates a slight vacuum effect in the lower levels of the house.
- The home begins pulling replacement air from outside through available openings.
That vacuum is part of what causes radon gas in homes. As the house tries to balance air pressure, it unintentionally draws radon gas through cracks, gaps and joints. The colder the weather, the stronger the stack effect tends to be, which is why many homes show higher radon levels during the winter months.
The stack effect is a natural process of airflow, but without a mitigation system in place, it’s also the mechanism that pulls radon indoors day after day.
Are There Other Sources of Radon?
While the soil beneath your home is the main concern, there are other sources of radon in homes as well. The two less common, but still important, additional contributors are well water and building materials.
Radon can dissolve into groundwater. When that water is used for showering, laundry or washing dishes, the radon may be released into the air. This typically affects homes with private wells more than those using municipal water.
Some natural building products, such as certain stones, concrete or brick, contain trace amounts of radon-producing minerals. These materials can emit very small amounts of radon, but they rarely create hazardous indoor levels on their own.
Although these sources exist, soil gas remains the primary and most significant cause of high radon levels in residential environments.
The Only Way to Know Is to Test Your Home
No matter where you live or how new your house is, radon risk is always a possibility. Homes with basements, crawl spaces or slab-on-grade foundations can all experience elevated levels. Even neighboring houses can have drastically different readings.
Since radon is odorless, invisible and impossible to detect without equipment, health organizations such as the U.S. Environmental Protection Agency (EPA) and the Prevent Cancer Foundation recommend that every home be tested — ideally every two years, after major renovations or after installing a new HVAC system.
When assessing indoor air quality, it’s important to know your home’s actual radon levels and whether they fall above or below the EPA action level of 4 picocuries per liter (pCi/L). Anything at or above this number calls for a mitigation solution.
Simple Ways to Help Keep Radon Levels Low
While professional mitigation is the most effective way to reduce elevated radon levels, there are additional steps you can take to keep levels low:
- Improve ventilation: Increasing air circulation in your home helps reduce radon accumulation. Open windows when the weather allows or run fans to lower indoor concentrations.
- Seal cracks and gaps: Regularly inspect your foundation, basement walls, and areas around pipes or wiring for visible cracks or openings. Using appropriate sealants to close these small entry points can limit radon’s pathways into your home.
- Use radon-resistant construction techniques: If you’re building a home, ask your builder about installing vent pipes, vapor barriers or gas-permeable layers beneath the slab.
How SWAT Environmental Helps You Take the Next Step
Testing your home doesn’t have to be complicated. SWAT Environmental provides free, easy-to-use DIY radon test kits that give you accurate insight into your home’s radon levels.
If your test shows elevated levels, our certified mitigation professionals are ready to step in and help. Our team designs and installs permanent mitigation systems that reduce indoor radon levels and help keep your home safe in the long term. Every system is customized to your home, delivering maximum effectiveness and reliability.
Reach out to our team to get your radon mitigation quote today.
