Radon Testing Guide:
The Invisible Gas Killing 21,000 Americans Per Year
Radon is the #2 cause of lung cancer after smoking. You cannot see it, smell it, or taste it. The only way to know if your home has dangerous levels is to test. Here is exactly how — using EPA-approved methods.
First step: know your numbers
A continuous radon detector gives you real-time readings — no lab fees, no waiting.
This Airthings digital monitor tracks radon levels 24/7. Unlike one-time test kits, it shows you daily, weekly, and monthly averages so you can spot dangerous spikes the moment they happen.
Get the Radon Detector — See Your Levels Now →Why You Must Test — The Numbers That Matter
Radon Test Types — Which One to Use
| Feature | Charcoal Test Kit | Alpha Track (Long-Term) | Digital Monitor |
|---|---|---|---|
| Duration | 2-7 days | 90+ days | Continuous |
| Cost | $15-30 (one-time) | $20-40 (one-time) | $150-250 (reusable) |
| Accuracy | Good (snapshot) | Best annual average | Good (real-time trends) |
| Lab Required | Yes (mail-in) | Yes (mail-in) | No — instant results |
| Best For | Initial screening, home sales | Confirming borderline results | Ongoing monitoring, basements |
| EPA Approved | Yes | Yes | Varies by model |
How to Test — Step by Step
Short-Term Charcoal Test (2-7 Days)
- 1 Close all windows and doors 12 hours before starting. Keep them closed during the entire test. Normal entry/exit is fine.
- 2 Place the test kit in the lowest lived-in level of your home (basement if you spend time there, otherwise first floor). At least 20 inches off the floor, away from walls, drafts, and humidity.
- 3 Leave undisturbed for the required period (2-7 days depending on kit).
- 4 Seal the kit immediately after the test period ends. Record end date and time.
- 5 Mail to the lab the same day. Results arrive in 1-2 weeks.
Understanding Your Results
Low risk. Consider retesting every 5 years or using a continuous monitor for peace of mind.
Borderline. WHO recommends action at 2.7. Do a long-term follow-up test to confirm average exposure.
EPA Action Level. Install a radon mitigation system. The risk is equivalent to smoking 8-16 cigarettes per day.
EPA-Listed Radon Test Kit — Lab Fees Included
If you are not ready for a continuous monitor, start with this $20 EPA-listed charcoal test kit. Lab analysis is included. Results in days. No reason to wait.
Get the Radon Test Kit — $20 Could Save Your Life →When Should You Test for Radon?
Test RIGHT NOW if you...
- ✓ Have never tested your home
- ✓ Are buying or selling a home
- ✓ Just finished a basement or renovation
- ✓ Live below the 3rd floor of a building
- ✓ Have children sleeping in the basement
Retest every 2 years, or if you...
- ✓ Had a mitigation system installed (verify it works)
- ✓ Made major changes to HVAC or ventilation
- ✓ Had new construction nearby (can shift radon pathways)
- ✓ Noticed new cracks in your foundation
- ✓ Are on a different season (radon varies by season)
Frequently Asked Questions
What is a safe radon level?
There is no truly safe level. The EPA action level is 4.0 pCi/L, but the WHO recommends action at 2.7 pCi/L. Even the US outdoor average of 0.4 pCi/L carries some cancer risk. The goal is to get radon as low as reasonably achievable.
Can radon come through concrete floors?
Yes. Radon is a gas — it passes through tiny cracks, joints, and even the pores in concrete. It enters through foundation cracks, sump pits, crawl spaces, and construction joints. Even well-sealed homes can have high radon if the soil underneath has uranium deposits.
How much does radon mitigation cost?
A professional radon mitigation system typically costs $800-$2,500, with an average of $1,200. It uses a fan and pipe system to vent radon from under your foundation to above the roofline. Most systems reduce radon by 99% and run for pennies per day in electricity.
Is radon only a problem in basements?
No. Radon can affect any level of a home, though concentrations are usually highest in basements and ground floors. Even second-story rooms can have elevated levels. Test on the lowest floor where people spend significant time.
Radon Gas Hazard
Full health effects, sources, and EPA action steps
Carbon Monoxide
Another invisible killer — the other gas you must detect
Room Scanner
Find all hazards by room — basement, kitchen, bedroom
Radon Does Not Warn You. A Monitor Does.
Place it in your basement or lowest living area. Check the reading. If it is above 4.0 pCi/L, take action immediately. This is not something to put off.
Get the Continuous Radon Monitor — Stop Guessing →