Radon is the maintenance issue with no symptoms. It has no smell, no taste, and no visible sign. Nothing in a property tells you it is there, and no resident will ever submit a maintenance request about it.
It is also, according to the EPA, a leading cause of lung cancer in the United States and the leading cause among people who have never smoked. That combination — serious risk, zero warning signs — is exactly why it gets ignored, and exactly why a responsible owner should test.
Quick Answer
Radon is a naturally occurring radioactive gas from uranium decay in soil and rock that enters buildings through foundation contact points. The EPA recommends taking action at 4 picocuries per liter (pCi/L) or above, and says reducing levels between 2 and 4 pCi/L is worth considering. Testing is inexpensive; mitigation typically uses sub-slab depressurization and is a routine, effective fix. Test the lowest livable level, and use a certified professional or a quality test kit.
How It Gets In
Radon forms underground and moves upward through soil. Buildings tend to be at slightly lower pressure than the ground beneath them, which draws soil gas in through any opening in the foundation:
- Cracks in slabs and foundation walls
- Construction joints where the slab meets the wall
- Gaps around plumbing and utility penetrations
- Sump pits and floor drains
- Crawl space floors, particularly exposed earth
- Block wall cavities
Because the mechanism is pressure-driven, radon levels are highest in the lowest occupied level and generally decrease on upper floors. They also vary with weather, season, and how the building is operated — which is why testing conditions matter.
Two things that surprise owners:
You cannot predict it from the neighbors. Radon levels vary house to house, sometimes dramatically between adjacent properties, because the soil, the foundation, and the building’s pressure behavior all differ. A neighbor’s clean test tells you nothing about your property.
New construction is not exempt. Tighter modern buildings can hold radon more effectively than drafty old ones. Age is not a proxy for risk in either direction.
Risk in Virginia
The EPA maps radon zones by county, reflecting predicted average indoor levels. Virginia contains counties across the range, with higher-potential areas concentrated in parts of the state’s western and northern regions.
Check your specific county’s designation through the EPA or the Virginia Department of Health, which operates a radon program with state-specific information.
But treat zone maps as background only. They are predictive averages across a county, not measurements of your building. A property in a lower-designated county can still test high, and a property in a higher-designated county can test clean. The map tells you the prior probability; only a test tells you the answer.
Testing
Short-term vs. long-term
| Short-term test | Long-term test | |
|---|---|---|
| Duration | Typically 2 to 90 days | More than 90 days |
| Best for | Screening, transactions, quick answers | Understanding true year-round average |
| Accuracy | Snapshot — affected by weather and conditions | Better reflects actual long-term exposure |
| Typical use for rentals | Initial screening at turnover | Follow-up where results are borderline |
A practical approach for a rental: run a short-term test at turnover when the property is empty and conditions can be controlled. If results are near or above the action level, follow up with either a long-term test or a second short-term test before deciding.
Testing conditions matter
- Test the lowest livable level — the lowest floor that is or could reasonably be used as living space.
- Maintain closed-house conditions for short-term tests: windows and exterior doors closed except for normal entry and exit, typically beginning 12 hours before and continuing throughout.
- Place the device correctly — away from drafts, exterior walls, windows, and high humidity, at roughly breathing height, per the kit instructions.
- Avoid testing during severe weather or unusually high winds, which can distort results.
- Do not disturb the device during the test period, and return it promptly for analysis.
For rentals, turnover is the natural window. The property is empty, you control conditions, and nobody is opening windows.
Who should test
Use a qualified professional, or a quality test kit from a reputable source. Radon measurement and mitigation professionals are credentialed through national proficiency programs, and the Virginia Department of Health can point you to state-specific requirements and provider information. For a real estate transaction, a professional measurement is generally the better choice.
Mitigation
The reassuring part: radon is a well-understood problem with a standard, effective solution.
Sub-slab depressurization is the most common approach. A pipe is installed through the slab into the material beneath, connected to a fan that draws soil gas from under the foundation and vents it above the roofline, where it disperses harmlessly. The system creates a pressure field beneath the slab that stops radon entering in the first place.
For crawl spaces, the usual approach is submembrane depressurization — a sealed vapor barrier over the earth floor with suction drawn beneath it.
Practical notes for owners:
- Systems are generally unobtrusive — a pipe and a quiet fan, often routed through a garage or along an exterior wall.
- Retest after installation to confirm the system is working.
- Retest periodically thereafter — every couple of years is a reasonable cadence — and after any significant work affecting the foundation or the building envelope.
- Fans have a service life and eventually need replacement. Include it in your maintenance plan.
- Do not disconnect the fan. Make sure residents understand it should run continuously, and that a monitor or manometer showing pressure is part of the system.
- Sealing alone is not mitigation. Sealing cracks helps a system work better but rarely solves the problem by itself.
The Crawl Space and Air-Sealing Interaction
Worth flagging because it connects to work owners are already doing.
Encapsulating a crawl space, sealing the building envelope, and improving insulation are all sensible for moisture and energy performance. They also change how the building handles soil gas. A tighter building can, in some circumstances, hold radon at higher concentrations than the leakier version did.
That is not an argument against efficiency work — it is a good argument for testing after any substantial envelope, crawl space, or foundation work. If you are planning crawl space encapsulation, a radon test before and after is inexpensive and tells you whether you have created a new issue. Our guides to crawl space moisture and attic insulation and ventilation cover the related work.
Landlord Considerations
Disclosure and testing requirements for rental housing are limited compared with the detailed federal framework that exists for lead paint, and requirements can differ by transaction type and locality. Confirm current obligations for your situation rather than assuming, and speak with a Virginia attorney if you are unsure.
Setting the legal minimum aside, there is a straightforward case for testing:
- It is inexpensive relative to the risk, and the risk is a serious health outcome.
- Mitigation is a known, bounded cost with a standard solution — not an open-ended problem.
- A tested property with a mitigation system is a selling point, both to residents and at eventual sale.
- Testing at turnover costs almost nothing operationally, since the property is already empty.
- Knowing is better than not knowing. An untested property is not a low-radon property; it is an unmeasured one.
If a resident asks about radon or requests a test, treat the request seriously and respond in writing. Dismissing it is both poor practice and a bad record to create.
For Renters
You can ask whether a property has been tested, and you can test yourself — kits are inexpensive and widely available. If you test and find elevated levels, share the results with your landlord in writing and ask about mitigation.
Because radon concentrates in lower levels, pay particular attention if you are renting a basement unit or a ground-floor unit over a crawl space, and especially if you spend significant time there. A basement bedroom or home office is where exposure accumulates.
The risk is cumulative over years rather than acute, so this is not an emergency — but it is worth knowing rather than assuming.
Putting It in Context
A brief note on proportion, because radon coverage can read as either alarming or dismissible and neither is right.
The risk is real and it is cumulative. Radon exposure raises lung cancer risk over years of exposure, and the risk is substantially higher for people who also smoke. This is not a hazard that harms you this week; it is one that accumulates over a long tenancy or a long ownership.
It is also entirely manageable. Unlike many environmental risks, radon has a cheap test and a standard, reliable fix. There is no diagnostic ambiguity — you get a number — and no uncertainty about the remedy. Very few property risks are this tractable.
The reasonable position for an owner sits between the two: not alarm, and not indifference. Test the property, act on the result, retest periodically, and move on. The whole exercise is a modest cost and a small amount of attention, and it removes a genuine unknown from the property.
For an owner with several properties, the efficient approach is to test each one at its next turnover rather than mounting a program. Within a couple of years you will have tested the portfolio at essentially no incremental operational cost, and you will know where you stand.
Frequently Asked Questions
What is radon?
A naturally occurring radioactive gas produced by uranium decay in soil and rock. It is colorless and odorless, and it enters buildings through foundation openings.
What radon level requires action?
The EPA recommends taking action at 4 pCi/L or above, and says reducing levels between 2 and 4 pCi/L is worth considering.
Is radon a problem in the Richmond area?
Levels vary house to house regardless of county designation. Check your county’s EPA radon zone as background, but only a test on the specific property gives you an answer.
How do I test for radon?
Use a quality test kit or a qualified professional. Test the lowest livable level under closed-house conditions, following the kit instructions on placement and duration.
How much does mitigation cost?
It varies with foundation type and system complexity. Get local quotes — it is a bounded, standard project rather than an open-ended one.
Does a radon system need maintenance?
Yes. The fan has a finite service life and eventually needs replacement, and you should retest after installation and periodically thereafter to confirm the system is working.
Can sealing cracks fix a radon problem?
Sealing helps a mitigation system work better but rarely solves the problem alone. Active depressurization is the standard solution.
Should I retest after crawl space encapsulation or insulation work?
Yes. Tightening the building envelope can change how it handles soil gas, so a test before and after substantial work is worthwhile.
Is new construction safe from radon?
No. Newer, tighter buildings can hold radon more effectively than older leaky ones. Age does not predict risk in either direction.
Testing Built Into the Turnover Routine
Radon is a good example of something easy to defer indefinitely because nothing ever prompts it. Mission Realty Property Management builds inspection and testing routines into turnover for managed properties across Richmond, Henrico, Chesterfield, and Hanover.
- Learn about our property management services
- Explore year-round maintenance planning
- See our owner resources
- Get a free rental analysis
- Or contact our team
This article is general guidance and is not legal or medical advice. Follow current EPA and Virginia Department of Health protocols, and use qualified professionals for measurement and mitigation.
