⚠️ Critical Health Alert
Radon gas causes 21,000 lung cancer deaths in the US every year—more than drunk driving. It's invisible, odorless, and could be accumulating in your home right now. The only way to know is testing.
Radon is a radioactive gas that seeps through foundation cracks from decaying uranium in soil. 1 in 15 homes has dangerous radon levels, regardless of geographic location or home age. This guide will show you exactly how to test your home, interpret results, and take action.
What You'll Learn:
- • Why radon testing is non-negotiable for every homeowner
- • The 2 types of radon tests and which to use
- • Step-by-step testing instructions
- • How to interpret your results
- • What to do if levels are high
- • Recommended test kits (with honest reviews)
Why You Must Test for Radon
Radon exposure is the #1 cause of lung cancer in non-smokers. The EPA estimates radon kills more Americans than house fires, carbon monoxide poisoning, and drowning combined.
The danger is accumulation. Radon doesn't cause immediate symptoms—it damages lung tissue over years of exposure. By the time symptoms appear (persistent cough, chest pain, difficulty breathing), cancer may already be advanced.
Who is at highest risk?
- ✓ Smokers - Radon + smoking increases lung cancer risk by 10x
- ✓ Basement dwellers - Radon concentrates on lower levels
- ✓ Zone 1 areas - EPA high-risk zones (though any home can have radon)
- ✓ Older homes - Foundation cracks worsen over time
Check your city's radon risk zone →
The 2 Types of Radon Tests
1. Short-Term Tests (2-7 days)
Best for: Initial screening, real estate transactions, quick answers
Short-term tests give you a snapshot of radon levels over 2-7 days. They're affordable ($15-40) and provide fast results, but can be influenced by weather conditions and seasonal variations.
When to use: If you've never tested, start here. If results show elevated levels (2 pCi/L or higher), follow up with a long-term test.
2. Long-Term Tests (90+ days)
Best for: Accurate annual average, post-mitigation verification
Long-term tests measure radon over 3-12 months, accounting for seasonal fluctuations. They provide the most accurate picture of your home's average radon level. The EPA recommends long-term testing after short-term results show 2-4 pCi/L (borderline range).
How to Test: Step-by-Step Instructions
Step 1: Choose Your Test Location
Test the lowest lived-in level of your home. This is typically the basement, but if you don't use your basement, test the main floor. Place the test kit in a room you use regularly (bedroom, family room, home office).
⚠️ Avoid: Kitchens, bathrooms, laundry rooms, or areas with high humidity
Step 2: Follow Closed-House Conditions
12 hours before and during the test:
- Keep all windows and exterior doors closed (except for normal entry/exit)
- Don't operate fans that bring in outside air
- Don't use fireplace or wood stove
- HVAC system can run normally
Why? Open windows dilute radon, giving falsely low readings.
Step 3: Place the Test Kit
Position at least 20 inches above the floor, away from:
- Drafts from doors, windows, or vents
- Direct sunlight
- High humidity areas
- Exterior walls (foundation cracks can cause anomalies)
Good spots: On a desk, shelf, or nightstand in the middle of the room
Step 4: Wait the Full Test Period
Leave the test undisturbed for the entire duration (2-7 days for short-term). Don't move it or peek at results early. Mark the end date on your calendar.
Step 5: Seal and Send (or Read)
For charcoal canisters: Seal immediately after test period ends and mail to the lab within 7 days. Results arrive in 1-2 weeks.
For digital monitors: Read the display immediately. Most show real-time levels plus short-term and long-term averages.
Understanding Your Results
Radon levels are measured in picocuries per liter (pCi/L) or becquerels per cubic meter (Bq/m³). The EPA action level is 4 pCi/L (148 Bq/m³).
Below 2 pCi/L - Low Risk
No action needed. Retest every 2 years or after major renovations.
2-4 pCi/L - Borderline
EPA recommends mitigation, especially for long-term exposure. Consider a long-term test (90+ days) to confirm annual average. If you smoke or have young children, strongly consider mitigation.
4-10 pCi/L - High Risk
Mitigation required. Contact certified radon professional within 6 months. Living in this home for years significantly increases lung cancer risk.
Above 10 pCi/L - Extremely High
Urgent action required. Mitigate within weeks. Consider temporary relocation until mitigation is complete. Levels this high are equivalent to smoking a pack of cigarettes daily.
What To Do If Levels Are High
Don't panic, but don't delay. Radon mitigation works—systems typically reduce levels by 90%+ and cost $800-2,500 depending on home size and foundation type.
1. Hire a Certified Radon Professional
Find contractors at nrpp.info (National Radon Proficiency Program). Get 2-3 quotes. Ask about warranty and post-mitigation testing.
2. Install Active Soil Depressurization (ASD)
Most common solution. A fan system vents radon from beneath the foundation before it enters your home. Installation takes 1 day. Fan runs 24/7 (costs ~$50-150/year in electricity).
3. Retest After Mitigation
Wait 30 days after system installation, then test again to verify levels dropped below 4 pCi/L. Most systems reduce to under 2 pCi/L.
4. Test Every 2 Years
Mitigation systems can fail (fan burnout, foundation settling). Retest every 2 years to ensure protection.
Best Radon Test Kits (Honest Reviews)
We've tested dozens of radon kits. These are the ones we actually recommend:
Airthings Wave Plus
Digital long-term monitor
If you're serious about radon monitoring, this is the gold standard. Provides real-time radon readings on your smartphone, plus tracks CO2, VOCs, temperature, and humidity. Long-term accuracy rivals professional lab tests.
Pros:
- ✓ Continuous monitoring (see radon levels anytime)
- ✓ Smartphone app with historical data and trends
- ✓ No lab fees - reusable forever
- ✓ Battery lasts 1.5 years
Cons:
- ✗ Higher upfront cost (~$250)
- ✗ Takes 7 days to calibrate initially
First Alert RD1 Radon Test Kit
Charcoal canister (mail-in lab)
EPA-approved short-term test. Simple, accurate, affordable. Place it, wait 48 hours, seal and mail. Results in 10 business days. Perfect for first-time testing or real estate transactions.
Pros:
- ✓ Inexpensive (~$15-25)
- ✓ Lab-analyzed (accurate results)
- ✓ Fast 48-hour test period
- ✓ EPA approved
Cons:
- ✗ Single-use only
- ✗ Waiting for lab results (10 days)
- ✗ Can't see results immediately
Corentium Home by Airthings
Digital short-term monitor
Middle-ground option. Battery-powered digital monitor shows radon levels on built-in display (no app required). Accurate after 7 days, more accurate after 2 months. Reusable.
Pros:
- ✓ See results instantly (after initial 7-day period)
- ✓ No lab fees, reusable
- ✓ Works without smartphone
- ✓ Portable - test multiple rooms
Cons:
- ✗ No smartphone app or data logging
- ✗ Results can fluctuate (less stable than Wave Plus)
Common Radon Testing Mistakes
❌ Testing with open windows
Fresh air dilutes radon, giving falsely low results. Keep house closed 12 hours before and during test.
❌ Only testing once
Radon levels fluctuate seasonally. Test every 2 years, or annually if first test showed 2+ pCi/L.
❌ Testing only the basement you never use
Test the lowest lived-in level. If you spend zero time in your basement, test your main floor instead.
❌ Assuming "low-risk zone" means safe
EPA zones are county averages. Individual homes in Zone 3 (low) can still have dangerous levels. Always test.
Final Thoughts
Radon testing is the cheapest insurance policy you'll ever buy. For $15-250, you can definitively know if your family is breathing radioactive gas 24/7. The alternative—ignoring it and hoping your home is safe—has killed 21,000 Americans this year alone.
Test your home this week. If levels are high, mitigate. It's that simple.
Check Your City's Radon Risk Zone
Get instant access to EPA radon data, local testing recommendations, and more hazard information for your area.
View Your City Report →📋 Affiliate Disclosure
Home Hazards Report is reader-supported. When you purchase radon test kits through our Amazon affiliate links, we may earn a small commission at no additional cost to you. We only recommend products we believe are effective based on EPA approvals, lab testing accuracy, and user reviews. Our testing guides and recommendations are independent.