Test Kit or Continuous Monitor?
Test kits ($15-30): Best for one-time screening (pre-purchase inspection, initial check after moving in). You'll pay $60-120/year if testing seasonally.
Continuous monitors ($150-300): Best for ongoing monitoring, tracking mitigation system effectiveness, or if you test more than 2-3 times per year. Pays for itself in 2-3 years.
Bottom line: If this is your ONLY test, use a test kit. If you want ongoing peace of mind, buy a monitor.
At a Glance
| Factor | Test Kit | Continuous Monitor |
|---|---|---|
| Upfront Cost | $15-30 per test | $150-300 one-time |
| Ongoing Costs | $15-30 every test | $0 (just batteries) |
| Test Duration | 2-7 days exposure + 5-10 days lab | Instant, continuous |
| Accuracy | ±25% (EPA certified) | ±10% (better) |
| Shows Fluctuations | No (snapshot only) | Yes (hourly/daily) |
| Best For | One-time screening | Ongoing monitoring |
Radon Test Kits: How They Work
Two Types of Test Kits:
1. Charcoal Canisters (Short-Term)
How it works: Charcoal absorbs radon for 2-7 days. You seal the canister, mail it to a lab, and get results in 5-10 days.
Pros:
- ✓ Cheapest option ($10-20)
- ✓ Quick exposure (2-4 days)
- ✓ EPA-approved for screening
Cons:
- ✗ Least accurate (±25-30%)
- ✗ Affected by humidity
- ✗ Snapshot only (misses fluctuations)
2. Alpha Track Detectors (Long-Term)
How it works: Plastic film records radon damage for 90+ days. You mail it to a lab for analysis. More accurate than charcoal.
Pros:
- ✓ More accurate (±15-20%)
- ✓ Not affected by humidity
- ✓ Captures seasonal variation
- ✓ EPA gold standard for long-term
Cons:
- ✗ Longer exposure (90-365 days)
- ✗ More expensive ($25-40)
- ✗ Still a snapshot (no daily readings)
⚠️ The Test Kit Problem:
Radon levels fluctuate daily based on weather, season, and home use. A 2-7 day test might catch a low period and give you false confidence, or catch a high spike and cause unnecessary panic. Test kits are snapshots, not the full picture.
Continuous Monitors: How They Work
What Continuous Monitors Measure:
Continuous radon monitors use alpha spectrometry or ionization chamber technologyto detect radon decay products in real-time. They update every 10 minutes to 24 hours depending on the model.
Advantages:
- ✓ Real-time readings: See radon levels right now
- ✓ Track changes: Know if opening windows helps
- ✓ Spot patterns: Radon high in winter? You'll see it
- ✓ Verify mitigation: Confirm system is working
- ✓ Unlimited tests: Check as often as you want
- ✓ Peace of mind: Continuous protection
Disadvantages:
- ✗ Higher upfront cost: $150-300 vs $15-30
- ✗ Requires power/batteries: Ongoing maintenance
- ✗ Learning curve: Need to understand readings
- ✗ Calibration drift: Accuracy decreases over 5+ years
- ✗ Can cause anxiety: Daily spikes might worry you
Popular Continuous Monitors:
Budget pick, built-in screen
App-connected, hourly updates
Premium, 6 air quality sensors
Long-Term Cost Comparison
Let's compare the 5-year cost of test kits vs a continuous monitor, assuming you test twice per year (recommended by EPA for homes in high radon zones):
Test Kits (2× per year)
Plus 2-week wait for results every test
Continuous Monitor
Plus unlimited tests, instant results
The Math:
Over 5 years, a continuous monitor costs about the same as 10 test kits ($200-300) but provides 365 days × 5 years = 1,825 days of continuous monitoring vs 10 snapshots. The monitor wins on value after Year 2.
Which Should YOU Choose?
Choose Test Kits If:
- ✓ This is your FIRST radon test (initial screening)
- ✓ You're buying a house and need pre-purchase documentation
- ✓ You only plan to test once or twice total
- ✓ Budget is extremely tight (under $30 available)
- ✓ You don't want to deal with batteries or devices
- ✓ You prefer lab-analyzed results over device readings
Best test kit: First Alert RD1 ($25 on Amazon) - alpha track detector, EPA-certified lab
Choose Continuous Monitor If:
- ✓ You plan to test 2+ times per year (monitor pays for itself)
- ✓ You want ongoing peace of mind (24/7 monitoring)
- ✓ You're verifying a radon mitigation system is working
- ✓ You want to understand seasonal radon patterns
- ✓ You live in a high-risk radon zone (Zone 1)
- ✓ You have kids/pregnant partner (extra caution warranted)
- ✓ You like data and want to track trends over time
Best monitor: Airthings Corentium Home ($179 on Amazon) - best value for continuous monitoring
Real-World Scenarios
Scenario: Buying a House
You're in contract to buy a home built in 1975. Home inspector recommends radon testing. Closing is in 3 weeks.
→ Use a test kit ($25-30). Fast turnaround (2-day exposure + 5-day lab = results before closing). If elevated, seller pays for mitigation. After moving in, buy a continuous monitor.
Scenario: Just Moved Into High-Radon Area
You bought a house in Iowa (Zone 1 - highest radon risk). You plan to live here 10+ years and have young kids.
→ Buy a continuous monitor ($179). Skip test kits—you'll want ongoing monitoring anyway. The monitor pays for itself vs repeated testing, plus gives you peace of mind with daily readings.
Scenario: Post-Mitigation Verification
You had a radon mitigation system installed ($1,500). Contractor says levels dropped to 1.5 pCi/L. You want to verify it's working long-term.
→ Buy a continuous monitor. You need ongoing verification that the system stays effective. A one-time test kit won't catch system failures. Monitor every 1-2 months to confirm levels stay low.
Scenario: Borderline Results (3 pCi/L)
Your test kit showed 3 pCi/L (just below EPA action level of 4). You're not sure if you should mitigate.
→ Buy a continuous monitor. 3 pCi/L on a test kit might be 2 pCi/L in summer and 5 pCi/L in winter. A monitor will show seasonal variation and help you make an informed mitigation decision.
Common Questions
Are continuous monitors as accurate as lab test kits?
Yes, often MORE accurate. Continuous monitors are ±10% while charcoal test kits are ±25-30%. Alpha track detectors (long-term kits) are ±15-20%, comparable to monitors. The main advantage of monitors is that they capture fluctuations, not just a snapshot.
Should I use both a test kit AND a monitor?
Some people do: test kit for official pre-purchase documentation (accepted in all states), then continuous monitor for ongoing peace of mind. But this is overkill for most people. Pick one based on your primary need.
Do I need to re-test every year with a continuous monitor?
No. That's the point of a continuous monitor—it's always testing. Just check your readings monthly. EPA recommends a follow-up test kit every 2 years to verify your monitor's accuracy (calibration check), but this isn't required.
What if my monitor shows different results than a test kit?
This is normal. Test kits are 2-7 day snapshots while monitors show averages. If they differ by less than 50%, it's expected variance. If the monitor says 1.5 pCi/L but the test kit shows 6 pCi/L, run another test kit to confirm—one device may be faulty.
Our Recommendation
First-Time Testing:
Start with a test kit ($25-30). If results are elevated (4+ pCi/L), then buy a continuous monitor to track mitigation effectiveness.
Get Test Kit ($25) →Ongoing Monitoring:
Buy a continuous monitor ($179). Pays for itself in 2-3 years vs repeated test kits, plus gives you 24/7 peace of mind.
Get Monitor ($179) →Can't decide? Start with a test kit, then upgrade to a monitor if results are borderline or elevated.