What’s Lurking Below Might Surprise You
What if the biggest health risk in your home isn’t mold or asbestos, but something you can’t see or smell? And what if it’s quietly building up right beneath your feet?
In this post, you’ll learn what a radon test is, how it works in basements, and what your results really mean—whether your home is near Red Rocks, in Highlands, or down by Confluence Park.
By the end, you’ll know how to confidently handle radon testing and take the right steps to protect your home and health before your basement finishing venture.
What Is a Radon Test for a Basement?
A radon test for a basement measures radon gas levels to detect harmful concentrations. Radon, a radioactive gas from soil and rock, seeps into basements through cracks and gaps. Testing is essential because radon is invisible and odorless. The EPA recommends testing all homes with basements to prevent long-term health risks.
How to Test for Radon in Your Basement
Short-Term Testing Kits
Short-term tests are a simple way to get a snapshot of the radon levels in your basement.
These kits usually stay in place for 2 to 7 days and are best used when the house is closed up—windows shut, exterior doors kept closed as much as possible, and no large fans running. This helps ensure reliable results by keeping outside air flow from affecting your indoor air.
You can buy a short-term radon test kit online, from local hardware stores, or sometimes get discounted test kits through national radon program services or your state radon office.
A typical kit includes a radon sampler, like a charcoal canister or an electronic device, instructions on setup, and a pre-paid envelope to send it to a lab for processing.
Make sure to follow the instructions closely, especially when it comes to the minimum test duration and proper placement in your basement.
Long-Term Testing Kits
If you’re looking for a more complete picture of your home’s radon exposure, a long-term test is the better option.
These kits measure radon over 91 days up to a full year.
Since radon levels shift with Colorado’s wild weather—dry fall air, heavy snowpack, and spring melt-offs—a long-term test gives a truer reading of what’s really happening under your basement slab.
Many use alpha-track detectors or digital devices that track radon continuously and provide more stable readings.
These kits are especially helpful if your short-term results come back near the EPA’s action level of 4.0 pCi/L.
By averaging out those ups and downs, a long-term test helps determine whether you actually need to take action or if your home stays within a safer range most of the year.
Test Placement Guidelines
To get accurate results, you need proper placement of your radon test kit.
The EPA recommends testing in the lowest lived in level of your home or any space that could be converted into a living area—like an unfinished basement.
Set the kit at least 20 inches off the floor, 3 feet away from windows or exterior doors, and not near vents, sump pumps, or high humidity spots like the laundry room or bathroom.
Avoid placing kits in crawl spaces, closets, or along exterior walls where air flow can interfere with measurements.
You’ll want to choose a central, open space in a room you use regularly, so the test reflects the air you and your family actually breathe.
When to Test
There’s no bad time to test your home for radon, but some moments are more important than others.
If your home has never been tested, if you’re about to finish your basement, or if you’re buying or selling, now is the time.
Even completed basements can develop new cracks or changes in pressure that invite radon in, so retesting every few years—or after major renovations—is smart.
Seasonally, the best time for radon testing is during colder months when homes are closed up and indoor air is more isolated from the outside. This gives a better sense of the highest possible radon levels you may be exposed to.
Fall is the best time to finish your basement.
What to Do After You Get Your Radon Test Results
Understanding Radon Levels
Once your test kit is sent to the lab, you’ll receive results measured in picocuries per liter (pCi/L).
The average radon level indoors across the country is about 1.3 pCi/L, while outdoors it’s around 0.4 pCi/L.
If your home measures 4.0 pCi/L or higher, the EPA recommends taking action.
Even at 2.0 to 4.0 pCi/L, there’s still an increased risk of lung cancer over time, so it’s smart to consider next steps to reduce radon levels.
Keep in mind that no amount of radon is considered completely safe.
Lower is always better, especially if your basement is used as a living area or if you plan to finish it.
The test results help determine whether your home needs radon mitigation or simple monitoring through another test later.
Next Steps Based on Results
If your short-term test comes back with high radon levels, you’ll want to confirm those results with a second test.
If the second reading—or a long-term test—still shows 4.0 pCi/L or above, it’s time to install a radon mitigation system. This system works by venting radon gas from beneath your foundation to the outside, preventing it from building up in your air.
After installation, it’s important to retest within a few months to make sure the system is working properly.
If your levels are between 2.0 and 4.0 pCi/L, you might decide to take preventive measures now or plan for mitigation later. This is especially relevant if you’re planning basement renovations that could change air circulation or foundation sealing.
How to Lower High Radon Levels
Radon Mitigation Systems
A radon mitigation system is designed to pull radon gas from below your home and vent it outside.
The most common type is called sub-slab depressurization, which uses a fan and vent pipe to create negative pressure under your floor slab or crawl space. This prevents radon from seeping up through cracks or openings in the foundation.
These systems are quiet, efficient, and run continuously.
Once a radon mitigation system is installed, it can reduce radon levels by up to 99% in some homes.
While sealing cracks and joints helps support the system, sealing alone isn’t enough to fix the problem.
For lasting results, professional installation and follow-up testing are key.
Cost of Radon Mitigation Systems
The cost to install a radon mitigation system can range from around $500 to $2,500, depending on your home’s size and layout. Most homes fall in the $1,000 to $2,000 range. Factors like foundation type, existing drain tiles, and how easy it is to run vent piping all play a role.
Some states and national radon programs offer free or discounted test kits or cost-sharing options to help homeowners manage the expense of fixing a radon problem.
A good installer will provide detailed test information and explain how the system will work in your home. They should also recommend a follow-up test after installation to confirm that the radon levels have dropped below the EPA’s action threshold.
Can You Mitigate Radon Levels Yourself?
While some homeowners choose to tackle small home improvement projects themselves, radon mitigation isn’t one to DIY lightly.
A system that isn’t properly sealed or vented could make things worse by pulling radon into the living space instead of venting it out.
The Environmental Protection Agency and National Radon Program Services recommend hiring a certified professional who knows how to determine the correct system for your home and ensure it’s safely installed.
Testing and Mitigating Radon in Water
Testing Radon in Water
In some homes, especially those using private wells, radon can enter through the water supply.
When this water is used for showering, laundry, or cooking, radon gas can escape into indoor air.
Water testing kits are available from home improvement stores, online retailers, or through state radon programs. They work much like air tests—collecting a sample and sending it to a lab for analysis.
If your water test shows high levels, it’s important to follow up with air testing, since inhalation is the greater risk. Combining both results helps you understand the full picture of your home’s radon exposure.
Options for Radon Mitigation in Water
There are two main ways to fix high radon levels in water: point-of-entry treatment and point-of-use treatment.
Point-of-entry systems treat the water before it enters your home, often with aeration systems that bubble air through the water and vent the gas outside.
Point-of-use systems treat water at a single faucet, such as in the kitchen.
Because inhaling radon gas from water poses a greater risk than drinking it, addressing the air first through a radon mitigation system usually takes priority. If both air and water contain elevated radon levels, a professional can help design a combined approach.
Legal and Professional Guidance for Radon Testing
Testing During Real Estate Transactions
When homes are bought or sold, radon testing is often part of the inspection process.
For reliable results, use a licensed radon measurement professional who follows EPA and national radon standards.
If elevated radon levels are found during real estate transactions, buyers and sellers can negotiate to have a radon mitigation system installed before closing.
Renting and Radon Testing
Tenants have the right to test their rental units for radon, especially if the property includes a basement or ground-level living area.
If high radon levels are detected, renters can contact their landlord to discuss mitigation options.
In many areas, landlords are required to address known indoor air hazards like radon.
Finding Certified Professionals
When it comes time to test your home for radon or install a mitigation system, certified professionals are your best resource.
Look for experts listed through your state’s health department, the EPA, or national radon program services.
Some training centers provide certification and maintain databases of qualified contractors.
A good professional will offer test information, perform follow-up checks, and document all measurements for your records.
Filing a Complaint
If you ever experience poor service, incorrect test procedures, or faulty system installation, you can file a complaint through your state’s licensing board or a national radon association.
These organizations maintain standards to protect homeowners and ensure that every radon mitigation system works as intended.
Keeping a record of your test results, serial number, and communication with your contractor can help resolve any disputes quickly.
Basement Bliss Starts With a Radon Test and Elevation Basements
Before planning the fun upgrades—like a wet bar for football Sundays or a home gym to balance out your Cherry Creek brunch routine—it’s worth making sure your basement is healthy from the ground up. Elevation Basements doesn’t perform radon testing or mitigation, but we always encourage homeowners to handle it early so there are no surprises once we begin your design or construction.
Our process is all about transparency, safety, and maximizing your basement’s potential—from your very first consultation to the final walkthrough. If you’re ready to start transforming your space, fill out our contact form today or give us a call.
