Radon Testing in Austin, Dallas, and Houston: What the EPA Map Gets Wrong About Texas

If you live in Austin, Dallas, or Houston and you have never tested your home for radon, you are operating on a twenty-eight-year-old assumption. The 1993 EPA Map of Radon Zones placed nearly every Texas county in Zone 3, the lowest predicted risk category. That single map shaped how homeowners, real estate agents, and even some inspectors have treated radon in Texas ever since. It also shaped what Texas did next, which is very little.

Texas does not require a state license to perform radon testing. Texas does not require radon testing during a real estate transaction. Texas no longer even manages its own radon program. That responsibility moved to Texas Tech University under an EPA Region 6 grant, and the university published a statewide map update in December 2021 using more than eleven thousand single-family residential test records collected between 2006 and 2020. The findings did not make the 1993 map look better.

The short version: the statewide averages are still modest, but they are not uniform, and the probability of finding elevated radon in a Texas home, particularly at the lowest livable level, is higher than the old map suggests. Individual homes are still the only thing that matters, because radon levels vary house to house, not just county to county. The only way to know what is in your air is to test it.

This guide walks through what radon actually is, why Austin, Dallas, and Houston each have a different risk profile despite sharing the same EPA zone, how testing works, what Texas does and does not require, and why working with an independent testing company matters in a state that leaves most of this to the homeowner.

What Radon Is and Why It Matters

Radon is a naturally occurring radioactive gas produced by the decay of uranium in soil, rock, and water. It is colorless, odorless, and tasteless. You cannot see it, smell it, or feel it. It rises out of the ground, seeps into buildings through foundation cracks, slab joints, sump pits, crawl spaces, and utility penetrations, and then accumulates in enclosed indoor air.

The EPA estimates that radon causes approximately 21,000 lung cancer deaths in the United States every year, which makes it the second leading cause of lung cancer overall and the leading cause among people who have never smoked. The American Lung Association estimates that roughly one in fifteen homes in the United States has radon at or above the action level. The U.S. Surgeon General has issued a formal warning on radon exposure.

Radon is measured in picocuries per liter of air, or pCi/L. The EPA action level is 4 pCi/L. If a home tests at or above 4 pCi/L, the EPA recommends mitigation. If a home tests between 2 and 4 pCi/L, the EPA recommends that the homeowner consider mitigation. The U.S. average indoor radon level in a single-family home is 1.3 pCi/L.

There is no safe level of radon exposure. Risk is cumulative. The longer you spend in a home with elevated radon, the more your lung tissue is exposed to radioactive particles that damage DNA and can trigger cancer decades later. This is why testing matters even when symptoms are absent. By the time symptoms appear, the exposure has already happened.

The Texas Radon Map You Know Is Outdated

The EPA published its Map of Radon Zones in 1993. It classified every county in the United States into one of three zones. Zone 1 counties have predicted average indoor radon levels above 4 pCi/L. Zone 2 counties have predicted averages between 2 and 4 pCi/L. Zone 3 counties have predicted averages below 2 pCi/L. The map was built from five data sources: indoor radon measurements, geology, aerial radiometric data, soil parameters, and foundation types. It was a reasonable attempt using early-1990s data.

Texas came out of that exercise looking clean. Almost every county landed in Zone 3. A handful of Panhandle counties were designated Zone 2. No Texas county was placed in Zone 1. That map is still what most people see when they search for Texas radon information. It is also three decades old, and it has not been updated by the EPA since.

In December 2021, an interdisciplinary research team at Texas Tech University published the Texas Indoor Radon Map 2020 Update under EPA Region 6 sponsorship. The researchers analyzed 27,145 radon test records from Alpha Energy Laboratories, narrowed to 11,504 single-family residential records, and broke the results out by physiographic subregion rather than just by county. The comparison with the old map is direct:

Measurement Context	Statewide Finding (2020 AEL Dataset)
First-floor mean radon level, Texas single-family homes	1.46 pCi/L (median 0.78 pCi/L)
Basement mean radon level, Texas single-family homes	7.85 pCi/L (median 3.26 pCi/L)
Physiographic subregions with first-floor probability of Rn ≥ 4 pCi/L greater than 10%	Central High Plains, Southern High Plains, Central Texas Uplift
Physiographic subregions with basement probability of Rn ≥ 4 pCi/L greater than 10%	All subregions statewide
Subregions showing 2 to 3 times higher levels than 1991 EPA screening data	Central Texas Uplift, Southern High Plains, Central High Plains

Basements are rare in Texas. Most homes sit on slab-on-grade foundations, especially on the Gulf Coast where the water table is shallow. That means the first-floor numbers are more representative of what most Texas homeowners experience. Those numbers are generally modest. But modest averages hide the fact that individual homes can test at any value, and the only way to know where your home sits is to measure it.

The Texas Tech researchers were explicit about this point. Their report states that there is no substitute for having a home tested, and their findings cannot and should not be used to predict the indoor radon concentration of any individual home, building site, or housing tract. Radon is local. It can be high on one street and low on the next.

Austin Radon Profile: Limestone, Granite, and the Capitol Building

Travis County sits at the edge of the Edwards Plateau, the Blackland Prairie, and the eastern Balcones Escarpment. The geology is layered limestone, clay soils, and, in pockets to the west, exposed granite outcrops associated with the Central Texas Uplift. That last detail matters for radon.

The Central Texas Uplift is one of the three subregions the Texas Tech 2020 update flagged as having indoor radon levels two to three times higher than 1991 screening data. The uplift extends from the Llano region westward, and it is the source of Granite Mountain, the Llano County quarry that supplied the sunset red granite used to construct the Texas State Capitol in the 1880s. That same granite was used in historic buildings across the state.

Granite contains uranium in trace amounts, and uranium decay produces radon. The Texas Capitol itself has measurable radon that builds up in its basement over weekends when the building is closed and HVAC systems cycle down. According to the Texas Department of State Health Services, Travis County has background radiation levels significantly higher than the statewide average, attributable in part to the presence of red granite throughout the county.

For an Austin homeowner, the practical implication is this: the regional geology matters, but it is not the whole story. A home in Tarrytown, Zilker, or Clarksville built on thin limestone over Cretaceous bedrock can behave very differently from a home in Cedar Park or Leander built on different soils with different foundation construction. Homes in Mueller, East Austin, Round Rock, Pflugerville, and Lakeway all share the same EPA Zone 3 designation and all sit on distinct geological substrates.

What Austin homeowners should take away:

• Travis County is classified Zone 3 on the outdated 1993 map, which predicts average levels below 2 pCi/L. Actual measured levels in specific homes can and do exceed that.
• Granite-bearing geology in the broader Hill Country is associated with higher radon potential. Homes built near or on granite substrate should be considered for testing on that basis alone.
• Austin’s hot summers drive extended air conditioning use. Tightly sealed, efficient homes can concentrate radon indoors during the months when windows stay closed.
• Rapid new construction in Austin over the past decade means many homes have never been tested, and builders are not required to test before turnover.

Radon testing is available for homes throughout Austin and Travis County, including the surrounding communities of Cedar Park, Round Rock, Pflugerville, Lakeway, West Lake Hills, and Bee Cave. AirMD provides independent radon testing in Austin using EPA-approved protocols and certified measurement professionals.

Dallas Radon Profile: The Blackland Prairie and What Local Testing Data Shows

Dallas County sits on the Blackland Prairie, a dense clay-soil belt that runs from north-central Texas down toward San Antonio. The soil is the kind of expansive clay that shifts with moisture, cracks in drought, and is famously hard on foundations. That cracking is relevant to radon because any fissure in a slab or at the base of a wall is a potential entry pathway for soil gas.

On the EPA’s 1993 map, Dallas County is Zone 3, predicted to average below 2 pCi/L. The Texas Tech 2020 update keeps Blackland Prairie first-floor averages in Zone 3, but it places basement averages in Zone 2, between 2 and 4 pCi/L. Very few Dallas homes have basements, so the first-floor data is the more practical reference point.

More telling is the data coming from local testing professionals. ScanTech Technical Consulting, an NRPP-certified measurement provider that has been testing homes in the Dallas-Fort Worth Metroplex for more than ten years, reports that approximately ten percent of homes tested in Dallas County exceed the 4 pCi/L EPA action level and an additional fourteen percent fall into the 2 to 4 pCi/L caution range. That adds up to roughly one in four homes testing at or near a level the EPA says warrants action or consideration. Similar patterns have been observed in Tarrant, Collin, and Denton counties.

This is a single firm’s dataset, not a randomized statewide sample, and it should be read as a signal rather than a population statistic. But it points in a consistent direction: individual homes in the Dallas area produce elevated radon readings often enough that “Zone 3, nothing to worry about” is not an adequate risk-management position for a buyer, seller, or long-term resident.

Dallas-specific considerations:

• Older homes in neighborhoods like Oak Cliff, Lakewood, Highland Park, and University Park have had decades to develop slab cracks, foundation movement, and compromised vapor barriers that can act as radon entry pathways.
• Newer construction across North Dallas, Frisco, Plano, Allen, McKinney, and the greater Collin County suburbs uses tight building envelopes for energy efficiency. Tight envelopes concentrate whatever soil gas does enter the structure.
• Real estate activity in the Dallas-Fort Worth market is high. Radon testing during the option period is increasingly common, but it is not mandatory, and many buyers skip it.
• Commercial buildings, including schools, daycare facilities, and medical offices, face specific duty-of-care exposures. Elevated radon in a commercial building where children or patients spend time is a liability issue, not just a health issue.

AirMD performs radon testing in Dallas and throughout the Metroplex, including Fort Worth, Arlington, Plano, Frisco, Irving, Richardson, Garland, McKinney, and surrounding communities in Dallas, Tarrant, Collin, Denton, and Rockwall counties.

Houston Radon Profile: The Gulf Coastal Plain and the A/C Season Problem

Harris County sits on the Gulf Coastal Plain, where the geology shifts to younger sedimentary deposits, clay soils, and a shallow water table. The Texas Tech 2020 update classifies the Coastal Prairie subregion’s first-floor radon levels as Zone 3, the lowest category. This aligns with expectations: the geology is less uranium-rich than the granite-bearing Hill Country, and the high water table limits how much soil gas migrates upward.

Houston’s building stock reinforces the pattern. Nearly every home in Harris County sits on a slab-on-grade foundation. Basements are almost nonexistent because excavating below the water table is impractical. Pier-and-beam construction exists in older neighborhoods like the Heights, Montrose, and parts of River Oaks, but it is the exception, not the rule.

This is where the “Houston doesn’t have a radon problem” logic starts to show its limits. Three factors complicate the assumption:

• Slab cracks and penetrations. A slab-on-grade foundation does not eliminate radon entry. It concentrates the entry points. Any crack, any plumbing penetration, any settlement fissure becomes a potential pathway. Houston’s expansive clay soils shift seasonally with rainfall and drought, and slab foundations move with them.
• Tight envelopes and long A/C seasons. Houston runs air conditioning for most of the year. Modern homes are sealed for efficiency. When a building stays sealed for months, whatever soil gas does enter accumulates rather than dissipates. The same HVAC design that keeps the humidity down can keep radon in.
• Individual home variability. Regional averages say nothing about a specific property. A home in Katy, Sugar Land, The Woodlands, Cypress, Pearland, or League City sits on a slab like every other home, but its specific soil, drainage, and construction details are unique. One home on a street can test low and the neighboring home can test high.

What Houston homeowners should take away:

• Average first-floor radon in the Coastal Prairie is below 2 pCi/L, which is generally reassuring but not a guarantee for any single home.
• The Texas Tech 2020 dataset for Coastal Prairie basements did show elevated averages, but basement data is limited in Houston because basements are rare. The practical interpretation is that the few homes with subgrade spaces, crawl spaces, or partial basements deserve attention.
• Post-hurricane repair work and foundation remediation can create new pathways. If a home has had significant foundation work after a storm, testing after the work is a reasonable step.
• Commercial and institutional buildings, including schools, medical facilities, and childcare centers, are subject to different testing standards and regulatory scrutiny than private homes.

AirMD provides radon testing in Houston and across Harris County, including The Woodlands, Katy, Sugar Land, Pearland, League City, Spring, Cypress, Kingwood, and surrounding Fort Bend, Montgomery, and Galveston County communities.

What Texas Does and Does Not Require

This is the section most Texas homeowners should read twice, because the regulatory picture is not what most people assume.

Regulatory Question	Texas
State license required to perform radon testing?	No. State endorses NRPP and NRSB certification but does not mandate it.
Radon testing required before a home sale?	No. Buyers must request and pay for testing themselves.
Radon named on the TREC Seller’s Disclosure Notice?	Yes, under §5.008. Seller must disclose known radon conditions, but is not required to test.
State agency managing the radon program?	Texas Tech University (transferred from DSHS under EPA Region 6 grant).
Radon testing required in schools and daycares?	Specific requirements flow from facility licensing, insurance, and duty-of-care frameworks rather than a single blanket state rule.
Building code requirement for radon-resistant new construction?	No state-level requirement. Not standard practice in most Texas municipalities.

Texas Does Not License Radon Testers

The state of Texas does not require a state-issued license to perform radon testing or radon mitigation. The Texas Radon Program, now operated by Texas Tech University, endorses certification through the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB), and it refers the public to those lists of certified professionals. Both NRPP and NRSB are private certification bodies. NRPP is recognized by the EPA and accredited under ANSI/ISO/IEC 17024.

The practical implication: in Texas, anyone can call themselves a radon tester. There is no state registry, no state exam, and no state enforcement. The burden is on the homeowner to verify that the person placing the device and interpreting the results holds a current NRPP or NRSB credential and follows the applicable ANSI-AARST measurement standards.

Texas Does Not Require Radon Testing in Real Estate Transactions

No Texas statute requires a home to be tested for radon before it is sold. The TREC Seller’s Disclosure Notice required by Texas Property Code Section 5.008 does specifically list radon as an environmental hazard the seller must disclose, alongside asbestos, lead-based paint, urea-formaldehyde, and mold. But the disclosure obligation is limited to what the seller actually knows. A seller who has never tested has nothing to disclose. The system rewards not testing.

For buyers, this means radon testing during the option period is almost always the buyer’s responsibility and the buyer’s expense. Buyers who care about this have to raise it themselves. Many do not know to ask.

Schools, Daycares, and Healthcare Facilities Face Different Standards

Commercial and institutional buildings operate under a different risk and compliance framework than private homes. Schools, hospitals, nursing homes, daycare centers, and assisted living facilities have duty-of-care obligations to test for radon and document the results. Some of these obligations flow from state licensing requirements for the facility type. Others flow from insurance, accreditation, or employer liability frameworks. Property managers and facility administrators who do not document radon testing expose themselves to both health-claim liability and regulatory action if an inspection or complaint surfaces it.

The Texas Radon Program Moved

As of the most recent state communications, the Texas Department of State Health Services no longer maintains the state radon program. Program responsibility transferred to Texas Tech University. The DSHS indoor radon page now redirects the public to the Texas Tech Texas Radon Information site. This is not a secret, but it is not widely known among real estate professionals or homeowners, and it matters because the state’s own public-facing radon information footprint is smaller than it was twenty years ago.

How Professional Radon Testing Actually Works

Radon testing is not complicated, but the execution is where accuracy is won or lost. Proper testing follows the ANSI-AARST standards for measurement protocols and quality control. There are two general categories.

Short-Term Testing

A short-term test runs between two and seven days. Short-term tests use either passive devices like charcoal canisters or liquid scintillation devices, or active devices like continuous radon monitors (CRMs). Continuous monitors record hourly readings, which allows the tester to detect tampering, closed-house condition violations, and anomalies. Short-term tests are standard in real estate transactions because they fit inside the option period.

Long-Term Testing

A long-term test runs from ninety days up to twelve months. Long-term tests use alpha track detectors or electret ion chambers. The advantage is that they capture seasonal variation. Radon levels move with weather, soil moisture, and heating or cooling patterns. A long-term test gives a more accurate picture of actual year-round exposure. A long-term test is the right call for a homeowner who wants to understand real-world risk rather than pass a transaction inspection.

Test Placement and Closed-House Conditions

A valid test requires closed-house conditions for at least twelve hours before testing begins and for the duration of a short-term test. Windows and doors stay closed except for normal entry and exit. HVAC systems run as they normally would. Devices are placed in the lowest frequently occupied level of the home, away from drafts, exterior walls, sumps, and sources of heat or moisture. Placement mistakes produce invalid results. This is why certified measurement professionals matter.

What a Proper Report Contains

A professional radon testing report includes the measurement result in pCi/L, the test device type and serial number, the calibration record, the date and time the test started and ended, the placement location, the closed-house condition certification, hourly data for continuous monitors, and a written interpretation with recommended next steps. If the result is above 4 pCi/L, the report should include guidance on confirmation testing and mitigation. If the result is between 2 and 4 pCi/L, the report should note the EPA’s recommendation to consider mitigation. A result below 2 pCi/L is reassuring but carries the standing recommendation to retest every two to five years or after significant changes to the building.

Real Questions Texas Homeowners Ask About Radon Testing

Do I really need radon testing if my county is Zone 3?

Yes, because the EPA zone is a county-level average based on 1993 data, not a prediction for your specific home. The EPA’s own guidance says the map should not be used to determine whether an individual home needs to be tested. The Texas Tech 2020 update confirms that every physiographic subregion in Texas has measured radon values above 2 pCi/L in at least some homes, and the probability of finding 4 pCi/L or higher in a Texas basement exceeds ten percent statewide. Testing is the only way to know where your home falls.

Is radon really a problem in Austin, Dallas, or Houston?

It can be, and the reasons differ by city. Austin has pockets of granite-bearing geology that elevate radon potential in specific neighborhoods, along with a documented Capitol-building radon profile driven by the red granite sourced from the Central Texas Uplift. Dallas sits on Blackland Prairie clay soils that crack with seasonal moisture changes, creating foundation entry pathways. Local certified testers in the DFW Metroplex report that roughly one in four homes they test falls at or near levels where the EPA recommends action or consideration. Houston’s Coastal Prairie geology produces generally lower averages, but slab-on-grade construction, tight HVAC-sealed envelopes, and long air-conditioning seasons can concentrate whatever radon does enter. Individual homes vary.

My home is brand new, do I still need to test?

Yes. New construction is not radon-resistant by default in Texas. Some builders install passive radon-ready rough-ins if the client requests them, but this is not standard practice and not required by code in most Texas municipalities. Newer homes are typically built with tighter envelopes for energy efficiency, which can increase indoor radon concentration if any soil gas is entering. Testing after a home is finished and occupied is the only way to verify actual levels.

We are buying a house and the option period is short, what can we do?

A short-term radon test using a continuous radon monitor can deliver results within forty-eight to ninety-six hours of placement. For most Texas option periods, that fits. The key is to get the test scheduled on day one of the option period, not day six. If the result is elevated, the buyer has room to negotiate mitigation as a condition of closing. Sellers typically respond reasonably to documented radon findings because mitigation is a solvable, priced problem, not a dealbreaker.

How often should I retest if the first result was low?

Every two to five years, or sooner if you have made significant changes to the home. Radon levels change over time. Foundation settlement, new cracks, HVAC renovations, additions, new windows, new sealing, and even major landscaping changes can alter the radon profile of a home. The EPA recommends retesting after any major structural renovation.

What happens if my home tests above 4 pCi/L?

A confirmatory test is the first step, either a second short-term test or a long-term test, to verify the initial reading. If the elevated level is confirmed, mitigation systems, most commonly active soil depressurization systems, are highly effective. Properly installed systems routinely reduce indoor radon levels by ninety percent or more. Mitigation costs in Texas typically range from under one thousand dollars to a few thousand, depending on foundation type and design complexity. Elevated radon is a solvable problem. The only unsolvable version is the one nobody tested for.

Who should test a commercial property, school, or daycare?

A certified radon measurement professional operating under ANSI-AARST commercial measurement standards (MAMF or MALB), not a residential tester working outside their scope. Commercial testing involves more devices, specific placement protocols based on floor plan and occupancy patterns, and documentation requirements appropriate to the building type. Schools and large buildings have their own standard, ANSI-AARST MAMF-2019, and testing results go into records that may be subject to regulatory review or insurance scrutiny.

Why Independent Testing Matters

There is a structural problem embedded in how radon services are delivered in most of the country, and Texas’s lack of regulation makes it sharper here than in states with licensing. The problem is simple: when the same company tests your home and also sells you the mitigation system, the incentives are misaligned.

A tester who also does mitigation has a financial reason to find a problem. A mitigator who also does post-mitigation clearance testing has a financial reason to find that the system worked, whether it fully did or not. These conflicts do not mean every combined provider is dishonest. Most are not. But the incentive structure creates the possibility of disputed results, and in a home sale or a commercial due-diligence context, disputed results cost money and time.

An independent testing company does not sell mitigation. It does not install radon reduction systems. It does not have a downstream product to upsell based on the test result. Its only deliverable is an accurate, properly documented measurement, and its reputation depends on nothing more or less than that. For real estate transactions, commercial due diligence, insurance claims, and litigation, an independent measurement carries evidentiary weight that a mitigator’s measurement cannot.

AirMD is an independent environmental testing company established in 2007. AirMD does not perform remediation of any kind. The company’s testing services span mold, asbestos, lead, radon, VOCs, formaldehyde, water quality, and broader indoor air quality assessments, and in every category the positioning is the same. Testing is the deliverable. The homeowner or property owner decides what to do next, with no commercial interest on the testing side pushing a particular outcome.

For a Texas homeowner operating in a state that does not license testers, does not require real estate radon testing, and does not actively maintain its own radon program at the state level, the independent testing standard is not a premium feature. It is the baseline that responsible homeowners should require.

Frequently Asked Questions

Is radon testing required by law in Texas?

No. Texas does not require radon testing for homes, and no state license is required to perform radon testing. Schools, daycares, healthcare facilities, and similar institutional buildings face different standards driven by facility licensing, insurance, and duty-of-care obligations.

What is the EPA action level for radon?

4 picocuries per liter of air (pCi/L). The EPA recommends mitigation at or above this level. Levels between 2 and 4 pCi/L should be considered for mitigation. The U.S. average indoor level is 1.3 pCi/L.

How long does radon testing take in Austin, Dallas, or Houston?

Short-term tests run two to seven days. Continuous radon monitor tests can produce valid results in forty-eight to ninety-six hours. Long-term tests run ninety days or longer and capture seasonal variation.

Can I use a DIY radon test kit?

Consumer kits can produce accurate results if placement and closed-house conditions are handled correctly. For real estate transactions, insurance claims, or commercial due diligence, a professional test using certified equipment and documented protocols is the defensible standard.

Does homeowners insurance cover radon mitigation?

Generally no. Radon is considered a naturally occurring condition rather than an insured peril, so mitigation is typically an out-of-pocket homeowner expense. Some warranty programs and new-construction builder policies include partial coverage, but this is the exception.

Will a radon test delay my home closing?

Not if it is scheduled early in the option period. A continuous monitor can deliver valid results within four days of placement, which fits inside nearly every Texas option period.

Should I test before or after my home inspection?

Both can be scheduled in parallel. Radon testing does not interfere with a general home inspection. Coordinating both at the start of the option period gives a buyer the most time to act on the results.

Who should I call for professional radon testing in Texas?

A certified measurement professional credentialed through NRPP or NRSB who follows ANSI-AARST standards and is independent of mitigation services. AirMD provides independent radon testing across Austin, Dallas, Houston, and the rest of Texas, with no remediation conflict of interest.

Schedule Radon Testing for Your Texas Property

The 1993 EPA radon map shaped how Texas thinks about radon, and it has not been updated in more than thirty years. The 2020 Texas Tech update tells a more nuanced story. Most Texas homes are not at elevated risk, but some are, and the only way to know which category your home falls into is to measure the air inside it.

Whether you are in Austin sitting on limestone and granite, in Dallas on Blackland Prairie clay, or in Houston on the Gulf Coastal Plain, the same principle applies. Radon is house-specific. Test your home. Get the results from a company that does not also sell mitigation. Act on the numbers.

To schedule independent radon testing in Austin, Dallas, Houston, or anywhere else in Texas, call AirMD at 1-888-462-4763 or submit a request online. Certified measurement professionals, EPA-approved protocols, no remediation conflict.