How to Test for Radon Yourself

Two Types of DIY Tests

Short-term charcoal canisters (48–96 hours)

Activated charcoal passively absorbs radon gas for 2–4 days. You mail the canister to a lab, and they measure the gamma radiation from radon decay products absorbed in the charcoal. Results arrive in 1–2 weeks.

• Cost: $15–$30
• Best for: Initial screening, real estate transactions with time pressure, confirming post-mitigation results
• Limitation: A snapshot, not a true annual average. Radon fluctuates — a short-term test captures only the conditions during those 48–96 hours

Long-term alpha track detectors (90–365 days)

An alpha particle track detector (typically a small plastic chip) records alpha particle impacts from radon decay over months. The cumulative count averaged over the exposure period gives a much more representative annual average.

• Cost: $25–$45
• Best for: Understanding actual chronic exposure, confirming that mitigation is working long-term
• Advantage: Seasonal variation is averaged out — you get the real number, not a weather-dependent snapshot

Step-by-Step: Short-Term Test

1. Buy a test kit

Look for kits listed with the NRPP or analyzed by an EPA-approved laboratory. Brands like Air Chek, RadonAway, and Accustar are widely used. Hardware stores (Home Depot, Lowe's) carry them, and they're available online.

2. Choose closed-house conditions

Close all windows and exterior doors at least 12 hours before testing and keep them closed during the test. HVAC can run normally — it doesn't affect results. Don't test during high-wind or severe weather.

3. Place the canister correctly

• Floor: Lowest livable level (basement > ground floor > don't test upper floors for initial screening)
• Height: 20 inches to 6 feet above the floor
• Location: Interior room used regularly. Avoid: near windows, exterior doors, sump pits, exterior walls, return air vents
• Don't disturb it: No vacuuming directly around it, no moving it

4. Run for 48–96 hours

Note the start and end time on the lab form. Some kits require exactly 48 hours; others are flexible within a 48–96 hour window.

5. Package and mail immediately

Radon decay products continue accumulating in the canister after testing ends. Some labs specify a maximum time between collection and postmark. Follow the included instructions.

6. Read your results

The lab reports in pCi/L (picocuries per liter):

• Below 2.0: Low — no action needed
• 2.0–3.9: Moderate — consider long-term test for confirmation
• 4.0 and above: EPA action level — mitigate
• Above 8.0: High — mitigate promptly
• Above 20.0: Very high — mitigate urgently

Step-by-Step: Long-Term Test

Same placement rules as short-term. The difference: you leave the detector in place for 90–365 days (typically 90 days minimum for meaningful results). Some labs include a reminder postcard for the retrieval date.

Long-term tests require no "closed-house" conditions — they run through all seasons and all conditions, which is exactly the point.

What Affects Accuracy

Will inflate readings:

• Testing during high-wind conditions (pressure changes accelerate soil gas entry)
• Placing near sump pits, floor drains, or significant foundation cracks
• Testing in winter in a tightly sealed home (radon is naturally higher in winter — fine for a long-term test, potentially unrepresentative for a short-term test)

Will deflate readings:

• Open windows or doors during the test period
• Testing in an unused area with little air circulation
• HVAC drawing outside air continuously

If your short-term test result is borderline (3.0–5.0 pCi/L), run a long-term test before deciding on mitigation. If it's clearly above 8.0 pCi/L, mitigate and use post-mitigation testing to confirm system performance.

After Mitigation

Test again 30 days after installation — with closed-house conditions, short-term kit, in the same location as the original test. This is your baseline post-mitigation level. Then test every 2 years with a long-term kit to confirm the system is still performing.

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