Radon in Florida Homes: Testing, Disclosure and Mitigation Explained

What is radon, and how does it get into a Florida home?

Radon is a radioactive gas produced as uranium in the earth breaks down. The Florida Department of Health explains that it comes from radium found in nearly all rock and soil, which is why there is no part of the state where radon is impossible. Outdoors, it mixes into the open air and stays at very low levels. Indoors, it can build up, because a house traps the gas that seeps into it.

Most of the radon inside a home comes from the ground beneath it. A house usually sits at a slightly lower air pressure than the soil under it, so it draws soil gas in through any opening it can find: cracks in the slab, the joints where slabs and walls meet, gaps around pipes and wires that come up through the floor, and openings left around drains, such as the space under a bathtub in many slab homes. Anything that pulls air out of the house, like bathroom fans, a clothes dryer or leaky return ducts, can add to that pull.

Building materials and water

Concrete, block and stone contain small amounts of radium too. The Department of Health says that for most Florida structures, building materials contribute less radon to indoor air than outdoor air does, but it also notes that homes built entirely of concrete with much less fresh air than recommended have had radon problems traced to the materials themselves. Water is the other path. Radon dissolves in ground water, and EPA explains that most of the risk from radon in water comes from gas released into the air during showers and other household use. If your home is on a private well and an air test comes back high, EPA suggests testing the water as well. If your water comes from a utility that draws on ground water, the supplier can tell you about radon in its water.

Is radon a problem in South Florida?

It can be, and the honest answer is that no map can tell you about your house. The Department of Health states that about 1 in 5 radon tests made in Florida are found to be elevated, with local rates ranging from as high as 7 in 10 to as low as 1 in 100, and that elevated levels have been reported in every region of the state. The figure describes tests that were made, not every home, but it is a clear reminder that Florida is not exempt.

The federal and state maps put South Florida in a lower-risk group, with one exception. EPA's Map of Radon Zones, developed in 1993, places Miami-Dade County in Zone 2, moderate potential, where the predicted county average is between 2 and 4 pCi/L. Broward and Palm Beach counties are in Zone 3, low potential, with a predicted average below 2 pCi/L. EPA prints a warning on the same map: it should not be used to decide whether an individual home needs testing, and all homes should be tested regardless of zone. The Department of Health adds that elevated radon has been found in homes in many Zone 3 counties.

Florida also has its own radon protection maps, published in 1995 to show where radon-resistant construction is recommended for new buildings. None of the three South Florida counties has a map for single-family homes and duplexes, which means no area there was flagged for extra radon-resistant features in houses. The state is careful about what that means: the maps describe radon potential for new construction on native soil, say nothing about the odds that an existing building has a problem and should not be used to predict indoor levels in a building that has not been tested.

The law treats our three counties as places worth checking. Under Section 404.056(4), schools, licensed day care centers and 24-hour care facilities in designated counties must be tested, and the Department of Health's list includes Broward, Miami-Dade and Palm Beach for all such facilities except buildings coded as single-family housing or duplexes. For a house, the takeaway is the one EPA repeats in every guide: radon varies from home to home, and a neighbor's result tells you nothing reliable about yours.

Why radon matters: what EPA and the Surgeon General say

The concern with radon is long-term exposure. The U.S. Surgeon General has warned that radon is the second leading cause of lung cancer in the United States, and EPA calls it the leading cause of lung cancer among people who have never smoked. In its 2003 risk assessment, EPA estimated about 21,000 radon-related lung cancer deaths a year in the United States. EPA also explains that radon and smoking together are an especially serious combination, and that the risk depends mainly on the radon level, the time spent in the home and smoking history.

EPA's position is that any radon exposure carries some risk and that no level is known to be safe, which is why its guidance talks about reducing levels rather than reaching zero. We are inspectors, not physicians. If you have health questions about radon or lung cancer, a doctor is the right person to ask, and the Department of Health's radon program can answer questions about testing at 1 (800) 543-8279.

The Florida radon disclosure in real estate contracts

If you have bought, sold or rented property in Florida, you have probably signed a paragraph about radon without much thought. It comes from Section 404.056(5) of the Florida Statutes, which requires this notice on at least one document, form or application signed at the time of, or before, a contract for the sale and purchase of any building, or the signing of a rental agreement for any building:

"RADON GAS: Radon is a naturally occurring radioactive gas that, when it has accumulated in a building in sufficient quantities, may present health risks to persons who are exposed to it over time. Levels of radon that exceed federal and state guidelines have been found in buildings in Florida. Additional information regarding radon and radon testing may be obtained from your county health department."

The statute exempts residential transient occupancies of 45 days or less, such as short vacation rentals. In practice, you will usually find the paragraph printed in the purchase contract itself, and our guide to whether a Florida buyer needs an inspection explains where it sits among the contract's other inspection terms.

What the disclosure does and does not mean

The notice is general. It tells every buyer and tenant that radon exists in Florida buildings and where to learn more. It does not say the house you are buying has radon, it does not mean the home was tested, and it does not require anyone to test. The Department of Health describes the requirement as disclosure, not testing, and notes that the Department of Business and Professional Regulation has fined real estate licensees who failed to provide it.

Sellers who already know their radon level are in a different position. Florida courts expect sellers to disclose known facts that materially affect a home's value and are not readily observable to the buyer, and our article on the pre-listing inspection for Florida sellers explains that duty in plain English. Whether a particular test result has to be disclosed is a question for a real estate attorney. EPA's own advice to sellers is practical: test before listing, fix the problem if there is one, and keep the results and the system paperwork, since a documented fix can be a selling point.

The EPA action level: what 4 pCi/L means

Radon is measured in picocuries per liter of air, written pCi/L, a unit of radioactivity. Florida's rules require certified testers to report radon results to clients in pCi/L, so that is the number you will see on a report. EPA estimates the average indoor level in American homes at about 1.3 pCi/L, and outdoor air normally holds about 0.4 pCi/L.

EPA's action level is 4 pCi/L: at that level or higher, EPA recommends fixing the home. Between 2 and 4 pCi/L, EPA says to consider fixing, because levels below 4 still carry some risk and many homes can be brought down to 2 pCi/L or less. Congress set a long-term goal of indoor radon no higher than outdoor levels, which EPA acknowledges is not yet achievable for every home.

Results close to the line deserve a careful reading. EPA gives the example of two short-term tests averaging 4.1 pCi/L: there is about a 50 percent chance that the home's year-round average is somewhat below 4. A long-term test, or a second short-term test, narrows the uncertainty. A radon number is also unlike a mold air sample. Radon results are read against a fixed EPA action level, while mold samples have no federal limit and are compared with outdoor air, as our guide to reading a mold lab report explains. If a musty smell is your real worry, a mold inspection with lab air testing answers a different question.

How radon testing works: short-term and long-term tests

Radon testing is simple in principle. A device sits in the home for a set time and measures the gas or its decay products, and the result is an average over that period. The devices fall into two groups.

• Passive devices need no power. They include charcoal canisters, alpha track detectors, electret ion chambers and charcoal liquid scintillation devices. After the exposure period they are sealed and sent to a laboratory for analysis.
• Active devices are continuous radon monitors that run on power and record levels over time. Their hour-by-hour record can reveal unusual swings that suggest a window was opened or the device was moved, and results are available when the test ends.

EPA divides tests by length. Short-term tests stay in the home from 2 to 90 days, and every test, whoever runs it, should last at least 48 hours. Long-term tests stay more than 90 days and give a better picture of the year-round average, because radon rises and falls from day to day and season to season.

Testing on your own schedule

For an owner who is not on a deadline, EPA's Citizen's Guide lays out a sequence. Start with a short-term test. If the result is 4 pCi/L or higher, follow up with either a long-term test, for the best picture of the yearly average, or a second short-term test, if you need an answer sooner. If the first result is more than twice the action level, take the second short-term test right away. Fix the home if the long-term result, or the average of the two short-term tests, is 4 pCi/L or more.

Testing during a sale

Real estate deadlines do not allow for a 90-day test, so EPA's Home Buyer's and Seller's Guide accepts three short-term options, each of which should include a way to prevent or detect interference.

EPA notes the trade-off: two devices side by side improve precision, while two tests one after the other better reflect the seasonal average. A certified tester can explain which suits your timeline.

Closed-house conditions and where the test goes

A radon result is only as good as the conditions during the test. EPA defines closed-house conditions as keeping windows closed, keeping doors closed except for normal entry and exit, and not running fans or other machines that bring in outdoor air. For tests of two to four days, those conditions should start at least 12 hours before the test begins and last until it ends. The Radon Testing Checklist in EPA's buyer and seller guide is the reference most testers follow:

• Close windows and exterior doors at least 12 hours before a short test, and keep them closed except for normal coming and going.
• Run the A/C normally. For tests under a week, operate only air-conditioning that recirculates indoor air. Equipment that brings in outdoor air, such as some fresh-air ventilators, falls in the category EPA says not to run, so ask the tester how to handle yours.
• Small exhaust fans run briefly, such as a bathroom fan during a shower, are acceptable.
• Do not run tests shorter than four days during severe storms or periods of high wind. In South Florida, that means rescheduling around a tropical storm.
• Place the device in the lowest level of the home that could be used regularly. In a slab house, that is the ground floor living area.
• Choose a room such as a living room, bedroom, den or playroom, not a kitchen, bathroom, laundry room, closet, hallway or stairway.
• Set it at least 20 inches above the floor, away from drafts, high heat, high humidity and exterior walls, where nobody will move it.
• If the house has a mitigation system, make sure the fan is running for the whole test.

Interference and why testers guard against it

In a sale, the seller's household lives in the house during a test the buyer is relying on, and opening windows or moving the device changes the result. EPA lists safeguards: monitors that record levels frequently, motion detectors, tamper-proof seals on windows, temperature and barometric pressure records, and a non-interference agreement signed by the occupants. EPA also notes that disturbing a test or closed-house conditions may invalidate the result and is illegal in some states.

Radon testing when you buy a home in Florida

For a buyer, radon is a timing question as much as a health question. A standard home inspection does not measure radon. Florida's standards of practice describe a visual inspection of the home's systems, and the InterNACHI standards list radon among the things an inspector is not required to determine, as our room-by-room inspection checklist explains. A moisture meter or a thermal imaging scan cannot see it either. Radon takes its own device, its own conditions and, in Florida, its own certification.

That means planning inside your inspection period. A short-term test needs at least 48 hours, plus 12 hours of closed-house conditions before it starts, plus lab time for passive devices. Schedule it in the first days of the contract, not the last. If you are booking your home inspection at the same time, ask us whether radon testing can be added to your inspection, so both are on the calendar from the start. Each service added to a visit changes the time and the fee, which our guide to home inspection pricing in Florida walks through.

If the seller already tested

EPA says a buyer may accept an earlier result, but should first find out who ran the test, where in the home it was placed, when it was done and whether anything has changed since, including renovations or changes to the A/C system. A new test makes sense if the old one is not recent (EPA gives about two years as an example), if the house was altered, if the checklist conditions were not met or if you plan to use a lower level than the one tested.

Write it into the contract

EPA suggests that the contract specify where the test will be placed, who will run it, what type of test it will be, when it will happen, how the buyer and seller will share the results and any costs, and when mitigation would be done and who would pay. Your agent or a Florida real estate attorney can tell you how that fits the contract you are signing.

If the result comes back high

EPA's advice is for buyer and seller to discuss the timing and cost of radon reduction, and it notes that most homes can be fixed for about the same cost as other common home repairs. Whether you ask the seller to install a system before closing, ask for a credit or do it yourself after moving in is a negotiation, and our guide to negotiating repairs after an inspection covers how Florida buyers handle those choices within the inspection period.

Slab-on-grade houses, block homes and condos

Most South Florida houses sit on a concrete slab poured directly on the ground, with no basement. That does not rule radon out. EPA lists homes with and without basements, new and old, drafty and well sealed, among the homes that can have a radon problem. In a slab house, the soil gas meets the slab directly, and the entry points are the cracks, joints and plumbing openings described above. The ground floor is where a test belongs.

Concrete block construction adds the building-material question. As noted earlier, the Department of Health has seen radon problems in homes built entirely of concrete with poor fresh-air supply, which is one more reason the only answer for a specific home is a test.

Condos and high-rise living

EPA and the Surgeon General recommend testing all homes below the third floor, which covers ground-floor and second-floor condo units. Height is not a free pass, though. The Department of Health reports that Floridians have found elevated radon levels through all floors of high-rise multi-family buildings, a problem it connects to all-concrete construction with limited fresh air. If you own or are buying a unit, a test of your own unit is the only reliable answer.

Fixing radon in a condo is also different from fixing it in a house. The slab, exterior walls and roof are usually part of the common elements, so any system that penetrates them typically needs the association's approval. Where the source is the concrete rather than the soil, a certified mitigation specialist may look at ventilation instead of soil suction. Ask the association whether the building has ever been tested. A condo unit inspection covers the inside of your unit, and the radon question runs alongside it.

Who can test for radon and install mitigation in Florida

Florida regulates radon work more closely than many states. Section 404.056(2) and Rule 64E-5.1203 of the Florida Administrative Code say that no person may test for or mitigate radon in Florida for a fee or other payment unless certified by the Department of Health. The rules create several categories:

• Radon measurement specialists perform measurements and advise on results, health risk and entry routes.
• Radon measurement technicians perform measurements, but only under the supervision of a certified measurement specialist.
• Radon mitigation specialists evaluate diagnostic tests, design systems and install them. To qualify, they need a Florida residential, building or general contractor's license or four years of relevant experience, along with approved training and a state exam.
• Radon mitigation technicians install systems under the supervision of a certified mitigation specialist.
• Certified measurement businesses and mitigation businesses are the companies that offer these services, each with a certified specialist on staff or on retainer.

Two exceptions are worth knowing. Owners and occupants may test their own home, which is why do-it-yourself kits are legal. And a business that is not certified may subcontract radon measurements to a certified business, as long as the client receives the certified business's complete report and the certified business interprets the results. Florida's rules also spell out what a certified measurement report contains: the name and certification number of the business, the name and certification number of the person who did the measurement, the device type and the start and end dates and times.

How to check a tester or mitigator

The Department of Health publishes lists of certified measurement businesses, mitigation businesses and individual specialists and technicians on its radon pages, and advises checking that a certification has not expired. It also cautions that home inspectors are not automatically radon certified. EPA points out a potential conflict of interest when the same company tests and installs the system, and recommends that the test after mitigation come from an independent, qualified tester.

Where Global Home Inspectors fits

Radon testing is not one of our standard services, and we do not install mitigation systems. If you are booking an inspection with us, ask us whether radon testing can be added to your inspection. Either way, the Department of Health's lists are the place to confirm that whoever runs your test or installs your system holds a current Florida certification.

What a radon mitigation system is: sub-slab depressurization

EPA calls active sub-slab suction, also known as sub-slab depressurization, the most common and usually the most reliable way to reduce radon. One or more pipes pass through the slab, or under it from outside the house, into the soil or gravel below. A fan connected to the pipe draws soil gas from under the house and releases it above the roof, where it dilutes quickly, while keeping the area under the slab at a slight vacuum so less gas enters the home. Often a single suction point is enough.

Before installing anything, a certified mitigation specialist or technician must perform a visual inspection and appropriate diagnostic tests, under Florida's rules. EPA describes one common diagnostic, a communication test, in which a vacuum is applied at one small hole in the slab while chemical smoke is watched at another to see how easily air moves underneath. Florida's rules require certified businesses to install systems according to the Florida Standard for Mitigation of Radon in Existing Buildings, which is published as an appendix to the Florida Building Code. These are the parts you should be able to identify on a finished system.

The test after the system goes in

EPA recommends a post-mitigation test within 30 days of installation, but no sooner than 24 hours after the system starts running with its fan on, using a two- to seven-day measurement under closed-house conditions. The installer may run its own check, and EPA recommends an independent measurement as well, either by a separate certified tester or by the owner with a qualified kit, to avoid any conflict of interest.

Living with a mitigation system: upkeep and retesting

A radon system asks for little attention, but it does ask for some. Look at the manometer regularly, the way you would glance at a smoke alarm light. If the liquid levels are even, or an alarm sounds, call a certified mitigation business. EPA notes that fans may last five years or more, that manufacturer warranties tend not to exceed five years, and that a fan may then need repair or replacement.

Retesting matters as much as the gauge. EPA recommends retesting at least every two years to make sure levels remain low, and again after major renovations, after changes to the A/C or ventilation, or if you start using a lower part of the house as living space. A fan-powered system also uses some electricity and can draw out a little conditioned air, which EPA lists among its operating costs.

If you sell a home with a system, EPA recommends telling buyers about it and giving them information on its operation and maintenance. Keep the installation records, the post-mitigation result and later retests in one place. During a home inspection, a visible system is noted like any other installed equipment, but only a radon test can say whether it is doing its job.

Radon-resistant construction in new Florida homes

Building radon resistance into a new house is cheaper than adding it later, EPA says, and the basic features are simple. A layer of gas-permeable material under the slab, often about four inches of clean gravel, lets soil gas move freely. Plastic sheeting on top of it, under the slab, helps keep gas out. Openings in the foundation are sealed. A three- or four-inch gas-tight pipe runs from the gravel layer up through the house to the roof, and an electrical junction box in the attic makes it easy to add a fan later. With a fan, the passive system becomes an active one.

In Florida, the state's standards for radon-resistant new construction are voluntary. They become mandatory in a county only if a majority of its permit-issuing agencies adopt them, and the protection maps show none of Broward, Miami-Dade or Palm Beach as recommended areas for single-family homes. Some builders include passive features anyway, so ask. Either way, EPA recommends testing every new home after people move in, including homes built to be radon resistant. Our guide to inspections for a newly built Florida home explains how the final walkthrough and the 11th-month visit fit around closing and the builder's warranty, and a radon test can be scheduled for the first months of occupancy.

Radon myths Florida homeowners hear

• "Florida doesn't have a radon problem." The Department of Health reports that about 1 in 5 radon tests in the state are elevated, in every region.
• "South Florida is low risk, so I can skip it." EPA's map places Miami-Dade in its moderate zone, and EPA says the map should never decide whether a home is tested. Elevated levels have been found in homes in low-potential counties too.
• "No basement, no radon." EPA says radon can be a problem in homes with or without basements. Slab homes are tested on the ground floor.
• "My neighbor tested low, so I'm fine." EPA is blunt: homes next to each other can have different levels, and only a test of your home answers the question.
• "Upper-floor condos are safe." The Department of Health has seen elevated levels on all floors of some high-rise buildings.
• "Sealing the cracks will fix it." EPA does not recommend sealing alone. It helps a suction system work, but it does not lower radon reliably by itself.
• "The granite countertops are the source." The Department of Health says no Florida radon mitigation has ever required removing a granite countertop. The soil under the house is the usual source.
• "The radon paragraph means the house was tested." It is a required notice in every Florida sale or lease, not a result.
• "A house with radon won't sell." EPA says that where radon problems have been fixed, home sales have not been blocked, and the added protection can be a selling point.

Radon and home inspections across South Florida

South Florida's housing stock covers every situation in this guide: slab-on-grade block homes from the 1950s to the 1970s across Broward and Miami-Dade, newer subdivisions in western Broward and Palm Beach County, and condo towers along the beach where radon can follow concrete rather than soil. The question is the same in each of them: what is the level in this home? We are based at 3610 N 65th Ave in Hollywood and inspect homes and condos across Broward, Miami-Dade and Palm Beach counties, with calls and texts answered seven days a week from 5 AM to 10 PM. When you call about your inspection, ask us whether radon testing can be added to your inspection, so you know your options before the inspection period gets short.

The bottom line

Radon in Florida homes is not a reason for alarm, but it is a reason to test. About 1 in 5 tests in the state come back elevated, the maps cannot speak for your house, and the disclosure in your contract is a notice, not a measurement. EPA's line is 4 pCi/L, with a fix worth considering from 2. A short-term test under closed-house conditions fits inside a typical inspection period if you schedule it early, and if the number is high, a sub-slab system installed by a Department of Health certified mitigation business usually solves it, with an independent retest to prove it. If you are buying or selling in Broward, Miami-Dade or Palm Beach County, call or text (954) 297-0317 or send us your inspection request, and ask us whether radon testing can be added to your inspection. You will have a firm price before anything is scheduled.

About the author

Peter Lemos, Certified Master Inspector®

Owner and lead inspector of Global Home Inspectors in Hollywood, FL. Peter holds InterNACHI certifications in wind mitigation, 4-point and mold inspection and has served Broward, Miami-Dade and Palm Beach counties since 2008.