Radon Questions for Home Buyers

Question 1

The house I'm buying tested at 4.8 pCi/L. Should I walk away?

Accepted Answer

That part should be handled through the transaction, lease, or property-management process, not as contract or lease advice from a mitigation contractor. The radon side is more straightforward: confirm the result if appropriate, understand whether an existing system works, and decide whether mitigation, passive activation, repair, or follow-up testing is needed for the specific property. A buyer, seller, tenant, or landlord should talk with the appropriate real estate, legal, property-management, or housing contact about deadlines, credits, contract rights, or lease obligations. Bill can help explain what the mitigation work would involve and what property details should be checked.

Question 2

The home I want to buy already has a mitigation system. Do I still need to test?

Accepted Answer

Yes, absolutely test. A mitigation system being present doesn't tell you anything about whether it's actually working. Systems can fail, fans can die, the pipe seal at the slab can degrade. A working system with a well-installed fan will typically show very low levels, so if you test and the numbers are still elevated, something is wrong with the system. Never skip the test just because there's a pipe sticking out of the floor.

Question 3

What is the radon action level for buying a house in Illinois?

Accepted Answer

The EPA sets the national action level at 4.0 pCi/L, and Illinois follows that same guidance. At or above 4.0 pCi/L, the EPA recommends fixing the home. Between 2.0 and 4.0 pCi/L, the EPA says the risk is lower but real, and mitigation is worth considering. Illinois is also a high-radon state, so elevated readings are common - it doesn't mean the house is a bad purchase, it just means you need a plan.

Question 4

The sellers mitigated before we put in an offer. Do I still need a new test?

Accepted Answer

Yes. You need to verify the mitigation actually worked. Pre-mitigation is meaningless to you without a post-mitigation test confirming the levels came down. Ask for the post-mitigation test report. If they don't have one, or the test was done too soon after install, you should get your own test done before closing.

Question 5

My realtor says radon is common and not to worry about it. Is that right?

Accepted Answer

Your realtor is right that radon is extremely common - especially in Illinois and across the Midwest. But "common" and "not worth worrying about" are two different things. Radon is the second leading cause of lung cancer in the US. The good news is it's fixable, and mitigation works reliably. You should absolutely worry enough to test, know the number, and make an informed decision. Don't skip it just because it's routine.

Question 6

The radon test came back at 2.8. My agent says it's fine. What do I think?

Accepted Answer

2.8 pCi/L is below the EPA's 4.0 action level, so your agent isn't wrong that it doesn't require action by EPA standards. But the EPA also says anything between 2.0 and 4.0 is worth thinking about, because the risk is real even if it's lower. I'd call it a heads-up, not an emergency. You could ask for mitigation, you could plan to retest after you move in, or you could install a long-term monitor to track it over time. It's your call - just don't assume 2.8 means zero risk.

Question 7

Who pays for radon testing when buying a house?

Accepted Answer

Typically the buyer pays for the radon test as part of their inspection package. In some cases the seller may have already done a test, but buyers should be cautious about relying solely on a seller-provided test - you didn't choose the tester, you don't know the conditions, and you have no way to verify protocol was followed. Paying for your own test gives you confidence in the result. It's a relatively small cost compared to what you're buying.

Question 8

I'm buying a 1960s ranch house. Should I expect high radon?

Accepted Answer

Ranch houses from that era often do have elevated radon, for a couple reasons. They tend to sit on slab or have older, cracked block foundations with lots of soil contact. They also often don't have the kind of tight construction that would limit soil gas entry points. Even so, age alone doesn't determine radon - the soil underneath matters more than the era of the house. Test it, and if it comes back elevated, know that ranch houses typically mitigate well.

Question 9

I'm buying a house with a finished basement. Should I request a radon test?

Accepted Answer

Yes, and finished basements are actually one of the reasons radon matters more than people think. Radon enters through the foundation, and if the basement is finished and used as living space - bedrooms, family rooms, offices - then you and your family are spending real time there. A finished basement doesn't make radon more dangerous, but it does mean you're more exposed to it if levels are elevated.

Question 10

The radon test was done 3 years ago and came back at 1.5. Is that still valid?

Accepted Answer

For a real estate transaction, a three-year-old test is generally considered too old. Real estate tests are typically supposed to be current - meaning done within the last twelve months at most, and ideally as part of this transaction. Beyond that, radon levels can change over time as the foundation shifts, the soil settles, or conditions around the home change. A fresh test is the right move.

Question 11

The listing says no radon issues detected. Does that mean they tested?

Accepted Answer

Not necessarily. That language often just means the sellers aren't aware of an issue - it doesn't confirm a formal test was done with a licensed device under proper closed-house conditions. It could mean they tested years ago, or tested informally, or simply never tested and are disclosing only what they know. Always get your own test done with a licensed professional. Don't rely on listing language as a substitute for a real test.

Question 12

I'm buying a new construction home. Should I test for radon?

Accepted Answer

Yes. New construction doesn't mean low radon. Radon comes from the soil, and the soil under a brand-new house is exactly the same soil it was before the house was built. Some new homes are built radon-resistant (RRNC - Radon-Resistant New Construction) with a passive pipe system, but passive doesn't mean working - it often needs a fan added to be effective. Test the house before you close, or shortly after, so you have a real number.

Question 13

Can I waive the radon contingency?

Accepted Answer

That part should be handled through the transaction, lease, or property-management process, not as contract or lease advice from a mitigation contractor. The radon side is more straightforward: confirm the result if appropriate, understand whether an existing system works, and decide whether mitigation, passive activation, repair, or follow-up testing is needed for the specific property. A buyer, seller, tenant, or landlord should talk with the appropriate real estate, legal, property-management, or housing contact about deadlines, credits, contract rights, or lease obligations. Bill can help explain what the mitigation work would involve and what property details should be checked.

Question 14

How long does radon mitigation take? Can we do it before closing?

Accepted Answer

Installation typically takes one day - a crew comes in, installs the fan and pipe system, seals any visible cracks, and it's done by end of day. Whether you can get it done before closing depends on how tight your timeline is. Most contractors can schedule within a week or two. Then you need a post-mitigation test, which takes a minimum of 48 hours. If there's enough runway, yes, it's very doable. If closing is in two weeks, it's worth trying. If it's in five days, you might be better off negotiating a credit.

Question 15

My inspector did a 48-hour radon test. How accurate is that?

Accepted Answer

A 48-hour short-term charcoal canister test is the standard for real estate transactions, and it gives you a reasonable snapshot of radon levels during those two days under closed-house conditions. It's not as precise as a 90-day test, but it's accepted across the industry as the standard method for purchase decisions. The key is that closed-house conditions were maintained - windows shut, limited opening of exterior doors - because that's what makes the result meaningful.

Question 16

Does radon testing have to happen during a certain season for it to be accurate?

Accepted Answer

Radon levels do tend to be somewhat higher in winter when houses are more closed up, but licensed short-term tests are designed to be conducted under closed-house conditions year-round to create a consistent baseline. You can test in any season. If you're doing a real estate transaction in July, that doesn't mean the test isn't valid - just make sure closed-house conditions were followed.

Question 17

I'm buying in the suburbs of Chicago. Is that an area with elevated radon?

Accepted Answer

The Chicago suburbs sit in an area where elevated radon is common. Northern and central Illinois have geological conditions - glacial deposits, certain soil compositions - that tend to produce more radon. That doesn't mean every house will test high, but testing is especially important in this region. Don't assume a house is fine just because it's suburban or because you've heard of neighbors with low levels.

Question 18

The radon test came back at 0.8 pCi/L. That's low, right?

Accepted Answer

Yes, 0.8 is a low result. The outdoor background level of radon is typically around 0.4 pCi/L, so 0.8 is only modestly above that. You don't need to take any action on a reading that low. Even so, radon levels can change over time as conditions around the house shift, so running a long-term monitor after you move in is still a reasonable thing to do if you want peace of mind.

Question 19

Should I trust the test the seller paid for, or should I get my own?

Accepted Answer

Getting your own test is always the better move in a real estate transaction. When the seller pays for the test, you have less visibility into whether the tester was truly independent, whether closed-house conditions were maintained, and whether the device placement followed protocol. Your own test, ordered through a licensed professional of your choosing, gives you a result you can rely on and stand behind.

Question 20

I asked for a radon test and got a number of 4.0 exactly. Does that require mitigation?

Accepted Answer

That part should be handled through the transaction, lease, or property-management process, not as contract or lease advice from a mitigation contractor. The radon side is more straightforward: confirm the result if appropriate, understand whether an existing system works, and decide whether mitigation, passive activation, repair, or follow-up testing is needed for the specific property. A buyer, seller, tenant, or landlord should talk with the appropriate real estate, legal, property-management, or housing contact about deadlines, credits, contract rights, or lease obligations. Bill can help explain what the mitigation work would involve and what property details should be checked.

Question 21

The seller says they've lived there 10 years with no health problems. Does that mean the radon is fine?

Accepted Answer

Radon doesn't cause symptoms you'd notice - no headaches, no sore throat, no fatigue. The only risk is long-term lung cancer from cumulative radiation exposure, and that takes years to develop. Ten years of living in a house with elevated radon doesn't produce any observable warning signs. So no, the fact that the sellers feel fine tells you nothing about whether the radon levels are elevated.

Question 22

My parents are buying a house and I'm worried about them being exposed to radon. The test came back at 5.0. What should I tell them?

Accepted Answer

Tell them that 5.0 pCi/L is above the EPA action level and the house should be mitigated before or shortly after they move in. The risk from radon is cumulative - the longer you're exposed and the higher the level, the greater the risk. Getting a mitigation system installed is straightforward and brings levels down dramatically. The important thing is not to let it sit. Encourage them to make it a condition of purchase or handle it as soon as they take possession.

Question 23

Is a radon level of 3.5 in the basement normal in Illinois?

Accepted Answer

3.5 pCi/L in the basement in Illinois isn't unusual - Illinois is a high-radon state and basement levels are typically higher than upper floors. It's below the EPA's 4.0 action level but in the range where the EPA says the risk is lower but still real. If the basement is living space, that's worth taking seriously. Whether you push for mitigation is up to you, but I wouldn't dismiss 3.5 as irrelevant.

Question 24

The listing says radon mitigation system installed. Is that a good sign or should I still be worried?

Accepted Answer

A mitigation system is generally a good sign - it means someone identified elevated radon and took steps to address it. But you still need a post-mitigation test to confirm it's actually working. Ask for documentation: the installer's report, the date of installation, and a post-mitigation test result. If there's no post-mitigation test on file, get one done before you close.

Question 25

My neighbor said they tested their house two streets over and it was fine. Does that mean this house is probably fine too?

Accepted Answer

Radon varies significantly even house to house on the same street. The geology under each lot, the specific foundation construction, and the way air moves through each home all affect radon levels independently. A neighbor's result tells you almost nothing about what the house you're buying will test at. Test the actual house.

Question 26

The house we're buying is in a neighborhood that just got built out, on fill dirt. Should I be concerned about radon?

Accepted Answer

Fill dirt is worth asking about, but radon depends more on what's underneath the fill than the fill itself. In general, radon comes from uranium and radium naturally present in soil and rock, and fill material varies widely in composition. If the area sits on radon-prone geology, the fill doesn't solve that problem. Test the house the same way you would any other.

Question 27

The sellers say they tested every year and it was always below 4. Do I still need my own test?

Accepted Answer

I'd still get your own test. You don't have visibility into their testing method, who conducted it, or whether conditions were consistent year to year. Annual testing is a responsible practice, but for a real estate transaction, a current test conducted by a licensed professional under your oversight is the standard you want. Their records are useful context, not a substitute.

Question 28

How much should I worry about radon in a house with a crawl space instead of a basement?

Accepted Answer

Crawl space homes can absolutely have elevated radon - radon enters through the soil-crawl space interface, and from there it migrates up into the living area above. The mitigation approach is a bit different (often a ground cover and depressurization under the cover rather than slab penetration), but it works. Test it the same way you would any other home, and if it's elevated, mitigation is very doable.

Question 29

What's the difference between a short-term and long-term radon test for a home purchase?

Accepted Answer

Short-term tests run 48 to 96 hours and are the standard for real estate transactions because they fit within inspection timelines. Long-term tests run 90 days or more and give you a more accurate picture of average annual exposure. For a purchase decision, you'll use the short-term test. Once you move in, following up with a long-term test or a continuous monitor gives you a more complete picture.

Question 30

Can the seller do the radon test themselves and send me the results?

Accepted Answer

No. In a real estate transaction, the test should be conducted by a state licensed radon measurement professional, not the seller. Having the seller conduct their own test creates an obvious conflict of interest and means the result can't be verified. In Illinois, state law and industry standards expect testing to be done by licensed, independent testers.

Question 31

Is it worth paying extra for a continuous electronic radon monitor vs. a charcoal canister for the inspection?

Accepted Answer

A continuous monitor gives you more information - it records readings hour by hour, so you can see whether conditions were maintained properly and whether levels fluctuated significantly. A charcoal canister gives you a single averaged result. Both are acceptable for real estate transactions. If you want more transparency in the data, a continuous monitor is worth the modest extra cost.

Question 32

The house tested at 4.3 and the sellers are offering to mitigate. What should I look for to make sure it's done right?

Accepted Answer

Ask that the mitigation be done by a licensed and licensed radon mitigation contractor, that a post-mitigation test be conducted at least 24-48 hours after installation (ideally with 30 days for meaningful results), and that you receive the full report from the mitigator. You want documentation of what was installed, where, and what the post-mitigation test result showed. If the result is still elevated after mitigation, that's a problem to address before you close.

Question 33

Can radon testing be done in winter? We're trying to close in January.

Accepted Answer

Yes. Radon testing can and should be done year-round, and winter is actually a consistent time to test because houses are typically buttoned up anyway, which mirrors the closed-house conditions the test requires. Cold weather doesn't compromise the test - in fact, you'll often see consistent results in winter because the house is naturally closed up.

Question 34

What do I do if the seller refuses to test for radon at all?

Accepted Answer

Then you test on your own dime as part of your inspection. You don't need the seller's permission to have the house tested - you just need the right to access during the inspection period, which your purchase agreement typically provides. A seller refusing to pay for testing is different from you being unable to get one done. Get the test, get the number, and make your decisions from there.

Question 35

Is 7.0 pCi/L dangerous? The house my parents want to buy tested that high.

Accepted Answer

The EPA considers anything at or above 4.0 pCi/L to warrant mitigation, so 7.0 is well into that range. The risk from radon is cumulative and long-term - it's not an acute emergency, but it's not something to sit on either. A well-installed mitigation system will typically bring 7.0 down to under 2.0 pCi/L, often much lower. Your parents should make mitigation a condition of the purchase and get a post-mitigation test before they move in.

Question 36

My agent is pushing me to waive all contingencies to compete. Should radon be one I keep?

Accepted Answer

I'd keep the radon contingency if at all possible, especially in Illinois. If you waive it and the house tests at 8 or 10 pCi/L, the mitigation cost lands entirely on you with no leverage. If you absolutely have to waive it to be competitive, at minimum still do the test so you know what you're getting into before closing. Waiving the contingency and skipping the test is the riskiest combination.

Question 37

The sellers are saying the mitigation system is only a year old. Should I believe them and not test?

Accepted Answer

Trust but verify. Ask for the installation paperwork and the post-mitigation test report. A one-year-old system should have documentation. If they can't produce it, that's a red flag. Even with documentation, getting a current test done gives you direct confirmation the system is still performing. Fans can fail. Pipes can get blocked. A quick 48-hour test tells you where things stand right now.

Question 38

What happens if closing already happened and then I find out radon is high?

Accepted Answer

At that point, the house is yours and the mitigation is your responsibility to arrange. That's exactly why testing before closing matters - once you've closed, your options narrow considerably. Get a licensed radon mitigation professional in to do an assessment and installation. The good news is that mitigation works regardless of when it's done. The house will still get fixed; you just won't have the seller contributing to the cost.

Question 39

I'm buying a two-story house with no basement - just a slab. Do I still need to test for radon?

Accepted Answer

Yes. Slab construction doesn't eliminate radon - radon enters through cracks and penetrations in the slab, through utility openings, and around pipes. It tends to be lower in slab homes on average, but not always. The first floor of a slab home is in direct contact with the foundation, so test it. Don't assume you're in the clear because there's no basement.

Question 40

We're looking at a house over a garage - no basement, no slab foundation touching soil in the living area. Is radon still a concern?

Accepted Answer

Homes built over garages with living space above grade typically have less radon risk because the living areas aren't in direct contact with soil gas, but it depends on the specific construction. If there's any basement or below-grade area connected to the living space, radon can still enter and accumulate. Even if it turns out to be low-risk, a quick test will confirm that and give you peace of mind.

Question 41

I'm buying a mobile home or manufactured home. Do those get radon?

Accepted Answer

Manufactured homes on permanent foundations with skirting can accumulate radon, particularly if they're set on a slab or have a crawl space. Homes on piers with open, well-ventilated undersides tend to have lower radon because there's less opportunity for accumulation. The specific setup matters. If the home is set on a full slab or enclosed crawl space, treat it the same as any other home and test.

Question 42

The house is a bi-level with the lower level half underground. How does that affect radon?

Accepted Answer

Bi-levels are common and can absolutely have elevated radon. The lower level, being partially below grade, is where radon is most likely to enter. If that lower level is finished and used as living space - bedrooms, family room - the exposure potential is meaningful. Test at the lowest livable level, which in a bi-level is typically that lower floor.

Question 43

I'm buying a 1970s split-level in the suburbs. Should radon be on my radar?

Accepted Answer

Yes. Split-levels from that era often have significant below-grade space and older foundations with more entry points for soil gas. They're common in Midwest suburbs and radon is a real consideration. Test it, and know that split-levels typically mitigate well - the multiple levels can make installation a bit more involved, but a skilled mitigator handles them routinely.

Question 44

The home I'm buying is a Victorian-era house from the 1890s, rubble stone foundation. What should I expect for radon?

Accepted Answer

Old stone foundations are among the least airtight foundation types - lots of gaps, mortar gaps, and soil contact. That can mean more radon entry points, though it can also mean more natural ventilation that prevents accumulation. You can't predict the result from the foundation type alone. Test it. If it's elevated, mitigation on a stone foundation is more involved than a modern poured concrete slab, but it's definitely doable.

Question 45

The house has a partial basement and part slab. Does that complicate radon testing or mitigation?

Accepted Answer

It can complicate both slightly. The test should still be placed at the lowest livable level - if the basement portion is used as living space, test there. Mitigation in a mixed-foundation home may require suction points in both the basement and the slab section to depressurize all soil-contact areas. A competent mitigator will assess the foundation layout and design accordingly. It's not a deal-breaker, just something to be aware of.

Question 46

I'm buying a condo on the third floor. Does radon apply to me?

Accepted Answer

For a third-floor unit, the soil contact is many floors away from where you live. Radon risk is dramatically lower in upper-floor condos. Radon can still enter through the building if the lower levels are highly concentrated and it circulates in HVAC systems, but this is generally not a significant concern for upper-floor residents. If you're in a ground-floor condo with slab contact, treat it more like a house.

Question 47

I'm buying a condo on the ground floor or in a garden-level unit. Is radon a concern?

Accepted Answer

Ground-floor and garden-level condos can definitely have radon concerns because you're in contact with or near the foundation. The building's common areas and the shared slab can be radon entry points. Testing is harder to arrange in a condo context and mitigation is a building decision, not an individual unit decision. If possible, have a radon professional assess the situation before you close, and factor in how building management handles indoor air quality issues.

Question 48

The house we want to buy is a new build in a subdivision. Do I need to ask the builder about radon?

Accepted Answer

Yes. Ask whether the home was built with RRNC - Radon-Resistant New Construction features - and get the specifics: is there a passive sub-slab vent pipe, and is there a junction box installed for easy fan addition? Then test the home. Some RRNC homes test fine without a fan; others benefit from activating the system. A test will tell you.

Question 49

The house is right next to a river. Does that mean radon is higher or lower?

Accepted Answer

Proximity to water doesn't reliably predict radon levels. Radon comes from uranium and radium in soil and rock, and floodplain soils have their own variable geology. In some areas, river valleys are actually lower radon zones; in others they're not. The only way to know is to test. Don't use geography as a substitute for measurement.

Question 50

I'm buying a house in a rural area of Illinois. Is radon more or less of a concern than in a city?

Accepted Answer

Rural or city doesn't determine radon - the underlying geology and the specific foundation do. Some rural areas of Illinois sit on high-radon geology; others don't. There's no blanket rule that rural means higher or lower. Test the house the same as you would anywhere. In Illinois overall, elevated radon is common enough that testing is the right default wherever you are.

Question 51

The house is on a hill. Does that affect radon?

Accepted Answer

Topography can have some effect on radon because hillside homes sometimes have more basement wall exposed to soil pressure and different drainage patterns, but it's not a reliable predictor. What matters is what's in the soil under the house, how the foundation is constructed, and how air moves through the home. Test the house - that tells you more than the landscape.

Question 52

We're buying a log cabin. Does radon apply to that kind of home?

Accepted Answer

Yes. If the cabin sits on a foundation - slab, block, or crawl space - radon can enter the same way it does in any home. The log wall construction doesn't change the foundation situation. Test at the lowest level of the cabin, and if it's elevated, mitigation is very doable even in non-traditional structures.

Question 53

The house I'm buying was previously used as a rental for 15 years. Does that affect radon risk?

Accepted Answer

The rental history doesn't affect the underlying radon level - radon comes from the soil, not from how the house was used. The rental use might mean more deferred maintenance and potentially more foundation cracks or gaps that serve as radon entry points, but that's speculative. Test it and let the result speak for itself.

Question 54

I'm buying a lake house in Wisconsin. Should I test for radon?

Accepted Answer

Wisconsin has significant radon risk in many areas, and lake houses are no exception - if anything, lake homes are sometimes used less frequently, meaning fewer windows open and potentially higher accumulation. Test it like any home. If it's a second property and you're spending extended time there, radon exposure still accumulates over time.

Question 55

Is radon worse in houses with French drains or interior drainage systems?

Accepted Answer

Interior drainage systems and French drains that connect to the sub-slab space can sometimes create pathways that allow radon-laden soil gas to more easily enter the basement. It depends on the specific installation. If the house has an interior drainage system, mention it to the radon professional doing the assessment - it's relevant context for both the test placement and potential mitigation design.

Question 56

The house was flipped and the flippers put in a new slab. Does a new slab mean lower radon?

Accepted Answer

A new slab is better than a cracked old slab for limiting radon entry points, but it's not a warranty of low levels. The soil under the slab still produces radon, and concrete isn't completely impermeable. Penetrations for plumbing and utilities are common entry points regardless of slab age. Test it and let the number be your guide.

Question 57

I'm buying in Chicago proper - do city homes have radon?

Accepted Answer

Yes. Chicago and its surrounding neighborhoods have elevated radon in many homes, particularly those with basements, which is most of them. Chicago houses, two-flats, three-flats, and older single-family homes all warrant testing. The fact that you're in a dense urban area doesn't reduce radon risk - it depends on the foundation, not the zip code.

Question 58

Is the radon map from the EPA accurate for deciding if I should test?

Accepted Answer

The EPA map is useful for understanding regional risk and setting expectations, but it's not a substitute for testing. The map shows predicted average indoor levels by county based on geologic data, aerial surveys, and measured home data. Any individual house can fall well above or below the county average. Use the map as context, not as a replacement for a test.

Question 59

I'm buying in the collar counties around Chicago - DuPage, Kane, Will. Is radon common there?

Accepted Answer

Yes. DuPage, Kane, and Will counties are in high-radon territory. These are among the areas where elevated indoor radon readings are commonly found. Testing is especially important in these counties, and mitigation is a routine part of the home purchase process for many buyers there.

Question 60

The radon test showed 4.2 in the basement and 1.1 on the main floor. Which number counts?

Accepted Answer

For a real estate transaction, the test is typically conducted at the lowest livable level, which is the basement - so 4.2 pCi/L is your number. The EPA action level applies to the lowest livable level of the home. The main floor reading is informative but it's the basement number that drives the decision. At 4.2, mitigation is warranted.

Question 61

The inspector placed the radon test on the second floor. Is that right?

Accepted Answer

No. Standard protocol for real estate radon testing is to place the device at the lowest livable level of the home - typically the basement or, if there's no basement, the first floor. A test placed on the second floor is not following standard protocol and likely underestimates the actual radon levels in the home. That test result is not reliable for making a purchase decision.

Question 62

Can I do a DIY radon test with a kit from the hardware store for a home purchase?

Accepted Answer

Hardware store charcoal test kits are designed for homeowner screening, not necessarily for formal real estate transactions. In Illinois, the real estate transaction test should be conducted by a state licensed radon measurement professional. A DIY kit result may not be accepted as an official real estate test, and there's no way to verify chain of custody or that protocol was followed. Use a licensed professional for the purchase test.

Question 63

The seller opened windows during the test because it was hot. Does that void the test result?

Accepted Answer

Yes, that's a serious problem. Opening windows during a radon test violates closed-house conditions, which are required to get a reliable result. Ventilating the house during the test artificially lowers the result. A test conducted with open windows is not valid for a real estate decision. You'd need a new test conducted under proper closed-house conditions with the seller or an agent maintaining those conditions for the full 48-hour window.

Question 64

What are "closed house conditions" and why do they matter for the radon test?

Accepted Answer

Closed house conditions mean all windows and exterior doors are kept closed except for normal entry and exit during the 48-hour test period. No fans or ventilation systems that draw outside air should be running. This standardizes the test so it reflects what radon levels are like in the home as it's actually lived in, not aired out. Without closed house conditions, the result is artificially low and meaningless for a purchase decision.