You can't see it, smell it, or taste it — and it might be collecting in your basement right now. Radon is a gas that shows up in homes across Maryland and DC, and testing is the only way to know if yours has a problem worth fixing.
A high radon reading isn't a cosmetic issue — it's a long-term health exposure, and the fix is usually straightforward once you know your actual number. This guide covers what radon is, how to test for it, what your result means, and when it's time to call a certified professional.
Radon Occurs Naturally in Maryland and DC Homes
Radon isn't a sign anything is wrong with your house — it's a gas that rises up from the ground through cracks in a foundation, gaps around pipes, or a sump pit. Maryland's health department describes it plainly: it is a colorless, odorless, invisible gas that occurs naturally in Maryland and many other states.1 The District isn't exempt either — DC's environment department notes that radon has been found in homes all over the United States, including the District of Columbia.2
Testing Is the Only Way to Know Your Number
There's no guessing your way to a radon answer. Maryland's health department is direct about it: you have to test your home for radon with a radon test kit.1 A short-term kit is inexpensive and simple — many hardware stores, home-improvement retailers, and county health departments carry them, and the process is just placing the kit, leaving it in place for the window the instructions specify, then mailing it to a lab.
What Your Result Means — and When to Act
Once your result comes back, there's one number to watch for: the EPA recommends homes be fixed if the radon level is 4 pCi/L (picocuries per liter).3 A reading right at that line is worth a second look rather than an immediate decision either way — a single short-term test is a snapshot, not a verdict, and weather, ventilation, and the season can all shift the number from one week to the next.
Maryland's own guidance on confirming a result is useful here, too: the higher your short-term results, the more certain you can be that you should fix your home.1 In practice, that means a reading that just barely crosses the line deserves a follow-up test before you commit to anything, while a result well above it is a clearer signal to move straight to fixing it.
Your Radon Testing Checklist
- Buy a short-term test kit from a hardware store, home-improvement retailer, or your local health department.
- Place it in the lowest level of the home you actually use.
- Close windows and exterior doors for the period the kit instructions specify.
- Mail the kit to the lab and wait for your result.
- If your result comes back high, test again before deciding on a mitigation system.
Why the Risk Is Worth Taking Seriously
The reason testing matters isn't abstract. Radon is the number one cause of lung cancer among non-smokers, according to EPA estimates,4 and nationally, radon is responsible for about 21,000 lung cancer deaths every year.4 None of that shows up as a smell, a stain, or a symptom you'd notice day to day — a test is the only way the risk becomes visible at all.
Common Radon Mistakes Maryland & DC Homeowners Make
- Assuming a newer home or an upper floor means radon isn't a concern.
- Skipping a follow-up test after one borderline short-term result.
- Testing with windows and doors open, which can skew the reading.
- Paying for a mitigation system before confirming the number with a second test.
- Hiring whoever shows up after a radon mailer instead of checking credentials first.
If You Need a Mitigation System, Hire Carefully
If your confirmed result sits at or above the EPA's action level, the fix is a mitigation system, not a DIY project. The EPA's own guidance is to contact your state radon program for help in finding qualified professionals in your state5 rather than hiring the first name that turns up in a search. A qualified installer can also walk you through what a system will actually involve for your specific foundation, since venting setups vary by house — a basement with a slab floor is a different job than a crawl space, and a good installer should be able to explain that difference to you before any work starts, not after.
Treat a radon mitigation bid the same way you'd treat any other home-repair estimate: ask what the system includes, how it's expected to bring your number down, and whether the installer will retest once it's in place to confirm it actually worked. A vague answer to any of those questions is worth a second opinion before you sign. Hiring any contractor for work on your home deserves the same scrutiny either way — see How to Vet a Contractor Before You Pay a Dime before you sign anything.
The Bottom Line
Radon is common, it's invisible, and testing for it costs very little compared to what you'd spend guessing wrong in either direction. Buy a kit, test the level you actually live in, and if your number comes back high, confirm it before you pay anyone to fix it.
Sources
- Radon — Maryland Department of Health
- DDOE Offers Free Home Radon Testing Kits — DC Department of Energy & Environment (DOEE)
- What is EPA's Action Level for Radon and What Does it Mean? — U.S. Environmental Protection Agency
- Health Risk of Radon — U.S. Environmental Protection Agency
- Radon Testing — U.S. Environmental Protection Agency