Why Test for Radon?

Radon is an invisible, odorless radioactive gas that causes approximately 21,000 lung cancer deaths per year in the United States. It’s the second leading cause of lung cancer after smoking, and the leading cause among non-smokers.

You cannot detect radon without testing. No home is immune — new homes, old homes, homes with basements, homes on slabs, and homes with crawl spaces can all have elevated radon levels. The EPA estimates that about 1 in 15 U.S. homes has radon at or above the action level of 4 pCi/L.

In Maryland and Pennsylvania, the risk is even higher. Approximately 40% of Pennsylvania homes and a significant portion of Maryland homes — particularly in Frederick County, western Maryland, and the I-270 corridor — test above the EPA action level.

Testing is the only way to know your home’s radon level, and it’s the first step toward fixing the problem if one exists.

Types of Radon Tests

Short-Term Tests (2–7 Days)

Short-term tests use small devices placed in the lowest livable level of your home for 2 to 7 days. They provide a snapshot of radon levels during the testing period. Common short-term test types include charcoal canisters, electret ion chambers, and continuous radon monitors (CRMs).

Short-term tests are useful for initial screening, real estate transactions, and post-mitigation verification. However, radon levels fluctuate with weather, season, and home ventilation, so a short-term test may not represent your annual average.

Long-Term Tests (90+ Days)

Long-term tests — typically alpha track detectors — remain in place for 90 days to one year. They provide a more accurate picture of your average annual radon exposure and are recommended by the EPA for confirming short-term results.

Continuous Radon Monitors (CRMs)

Professional testers often use continuous radon monitors that record radon levels hourly over a 48-hour period. CRMs detect tampering (opening windows, moving the device) and provide hour-by-hour data. This is the gold standard for real estate transaction testing.

DIY vs. Professional Radon Testing

DIY Test Kits — $15 to $30

Available at hardware stores and online. You place the device in your home, leave it for the specified period, then mail it to a lab for analysis. Results arrive by mail or email within 1 to 2 weeks.

DIY kits are a cost-effective screening tool, but they depend on proper placement and closed-house conditions. User error (placing the kit in the wrong location, not maintaining closed-house conditions, or disturbing the test) can produce inaccurate results. For help choosing the right kit, see our guide to the best radon test kits for home buyers.

Professional Radon Testing — $125 to $250

A certified radon tester places professional-grade equipment (typically a CRM) in your home, maintains chain-of-custody protocols, and provides a certified report. Professional tests are tamper-resistant and provide hourly data.

Professional testing is recommended for real estate transactions, when accuracy is critical, or when you want documentation that will hold up to scrutiny from buyers, sellers, or contractors.

How to Test Your Home for Radon

Whether you’re doing a DIY test or hiring a professional, these guidelines improve accuracy:

Test in the lowest livable level of your home — typically the basement if it’s used or could be used as living space. If you don’t have a basement, test on the ground floor.

Maintain closed-house conditions for at least 12 hours before and during the test. Keep windows and doors closed (normal entry and exit is fine). Don’t operate whole-house fans.

Place the test device at least 20 inches above the floor, at least 3 feet from exterior walls, and away from drafts, high humidity, and direct sunlight.

Don’t test in kitchens, bathrooms, or laundry rooms — moisture and ventilation make results unreliable.

Leave the device undisturbed for the entire testing period.

Understanding Your Radon Test Results

Radon is measured in picocuries per liter (pCi/L). Here’s how to interpret your results:

Below 2 pCi/L — Low risk. No immediate action needed. Consider retesting every 2 to 5 years since conditions can change.

2 to 4 pCi/L — Moderate risk. The EPA suggests considering mitigation in this range. The World Health Organization recommends action at 2.7 pCi/L.

4 pCi/L and above — Action recommended. The EPA action level is 4 pCi/L. At this level or above, the EPA recommends installing a radon mitigation system.

Above 8 pCi/L — Elevated. Mitigation is strongly recommended. At these levels, radon exposure poses a meaningful health risk, particularly for long-term occupants.

Above 20 pCi/L — Very high. Take action promptly. Consider temporary measures (increased ventilation) while arranging professional mitigation.

The important thing to understand: there is no known safe level of radon. Any reduction in exposure reduces risk. But the EPA sets 4 pCi/L as the practical threshold for recommending mitigation because effective systems can reliably achieve levels below this mark.

Radon Testing for Real Estate Transactions

Radon testing has become a standard part of home inspections in Maryland and Pennsylvania. If you’re buying or selling a home, here’s what to know:

For buyers: Request a professional radon test as part of your inspection contingency. If results are above 4 pCi/L, you can negotiate mitigation with the seller or request a price reduction. A professional CRM test is preferred for real estate transactions.

For sellers: Consider testing before listing. If levels are elevated, installing a mitigation system proactively removes a common negotiation obstacle and demonstrates that you’ve addressed the issue. A home with a documented mitigation system is easier to sell.

For real estate agents: Familiarize yourself with local radon data. In high-risk areas like Frederick County, MD or Lancaster County, PA, buyers increasingly expect radon testing as standard practice.

Recommended Radon Test Kits

Whether you need a quick screening or ongoing monitoring, these are the most reliable options available:

For Short-Term Testing (Home Buyers & Quick Screening)

First Alert Radon Gas Test Kit, RD1 — Simple charcoal-based kit. Results in 2–7 days through a certified lab. Best for: home purchases, first-time screening. (~$15)

For Continuous Monitoring (Homeowners)

Airthings Corentium Home 2 — A dedicated digital radon detector with Bluetooth connectivity. Tracks radon levels continuously with no lab fees or subscriptions. Best for homeowners who want reliable, ongoing radon awareness. (~$180)

Airthings View Plus — The most comprehensive Airthings monitor with 7 sensors (radon, CO2, humidity, temperature, PM2.5, VOCs, air pressure). Best for homeowners who want full indoor air quality tracking alongside radon. (~$299)

Shop Airthings radon monitors direct — Save 10% with code RADONSAFETY-10OFF at checkout. Also available on Amazon.

As an affiliate, we earn from qualifying purchases at no extra cost to you. RadonSafetyGuide.com participates in the Airthings affiliate program and the Amazon Associates program.

Get a Professional Radon Test

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Radon Testing in Your Area

Need a radon test in Maryland or Pennsylvania? Start with a DIY test kit or get connected to a certified professional in your area.

Maryland: Frederick · Hagerstown · Middletown · Thurmont · Emmitsburg · Brunswick

Pennsylvania: Harrisburg · Lancaster · York · Gettysburg

Illinois: Naperville · Hinsdale · St. Charles · Wheaton · Glen Ellyn · Downers Grove · Elmhurst · Barrington

Buying a home? See our complete radon testing guide for homebuyers — what to request, what results mean, and what to do if levels are high.

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Frequently Asked Questions About Radon Testing

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