Radon is a natural gas that comes from the breakdown of uranium in soil and rock. You cannot see or smell it, but it can build up inside homes. Basements are a common place for radon because they are below ground and often have cracks or openings where soil gases can enter. Long-term exposure to high radon levels can raise the risk of lung cancer, even for people who never smoke.
Why basements are at higher risk
When air pressure inside a house is slightly lower than the pressure in the soil, the home can “pull” radon in. Basements have more contact with the ground, and the concrete floor and walls can have small cracks that act like pathways. Sump pits, floor drains, crawl spaces, and gaps around pipes can also let radon enter.
How radon gets into a basement
Radon typically enters through:
- Cracks in concrete floors and foundation walls
- Construction joints, where the floor meets the wall
- Gaps around plumbing, wiring, or HVAC lines
- Sump pits and drains
- Crawl spaces with exposed soil
Even a well-built home can have radon, so the only way to know is to test.
Detection strategies: how to test for radon
Testing is simple and affordable. There are two main types:
- Short-term tests (usually 2 to 7 days): Good for a quick snapshot.
- Long-term tests (90 days to a year): Give a better picture of your average exposure.
Place the test in the lowest level of the home that is used regularly, often the basement. Keep windows and outside doors closed as much as possible during a short-term test. The U.S. Environmental Protection Agency recommends taking action if the radon level is 4.0 pCi/L or higher, and many families choose to reduce levels even if the result is between 2.0 and 4.0 pCi/L.
Prevention and reduction strategies
If you are building a home, you can include radon-resistant features like a gas-permeable layer under the slab, plastic sheeting, sealed foundation openings, and a vent pipe that can later be upgraded with a fan.
For existing homes, the most common and effective method is sub-slab depressurization. In this system, a pipe is installed through the basement floor into the gravel or soil below. A quiet fan pulls radon from under the house and vents it safely above the roofline. Other helpful steps may include:
- Sealing visible cracks and gaps (this helps, but usually is not enough by itself)
- Sealing and covering sump pits
- Improving basement ventilation in certain situations
After mitigation, it is important to retest to confirm the level dropped.
Protecting your family
Radon is a serious health risk because it can affect people over many years without any warning signs. The good news is that testing and fixing a radon problem is very doable. A professional can help you choose the right test, interpret the results, and install a system that fits your home.
Recommended local help
If you live in Colorado and want expert guidance, Absolute Radon Safety of Colorado can help protect your family from the dangers of radon gas. They can provide radon testing and proven mitigation options, and they can explain each step in clear, practical terms so you know what is happening in your home and why.
