Radon Retesting?

Looking for opinions here…

Our weather patterns are somewhat unpredictable. I try to avoid doing a Radon test when strong storms are forecast, but sometimes they occur despite a “20% chance of light showers”.
I’ve had several such incidents occur during a Radon test and the overall result coming back over 4piC/L.

I flag those results as being unreliable because of storms and/or heavy rain and indicate the need to re-test.

Looking for opinions about whether I should be re-testing for free or charge for the retest. One one hand, I sold a service that I was not able to deliver. On the other hand, I don’t have control over the circumstances. I wonder if a disclaimer added to the testing agreement would help.

-Todd Thuss, CPI
Integra Inspection Services, LLC
Huntsville, AL

Results are what they are, you don’t control the weather and whats more if the results fluctuate upwards during certain times of the year shouldn’t the buyer know what the highs are instead of the lows. If you retest for free you wont be in business long.


Thanks for the reply, Alan. I am asking because I had a local mitigator say he wouldn’t charge for a re-test. That got me thinking.

That is the problem with short term testing. I would recommend that if you get elevated results that a longer term test be done to confirm original results.

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Are you using CRM’s or charcoal kits? Here is an advantage for CRM’s…if storms move through you can extend the test to 96 hours.

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So if the weather is good, and you get better results you accept that as indicative of average Radon for that property? What if it storms most of the year, would you retest because you had good weather for two days? Alan got it right, you don’t control the weather. The only reason the mitigator does a free retest is because he’s going to sell them an expensive mitigation system! Its a sales tool!

Electrets can be extended to 96 hours as well so I don’t know that CRMs are an advantage. 96 hours is typically too long for a Real Estate transaction anyway.


As Bob indicated, the mitigator is wanting to sell his system and he’ll make more than enough to cover a retest.

Use YOUR business model not his. :smile:

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A Mitigator should not be the one doing the Testing except for their own internal use. It is a clear conflict of interest for them to do the initial testing (to sell their service) or Test after, to verify Their System is working (trust me)… It is the same reason we should not be fixing things on homes we inspect. Robert is correct, when the sale of a house is involved longer tests are just not feasible in most cases.

If I remember correctly the instructions on charcoal kits say up to 96 hours for testing. Of course the benefit of a CRM would be that you could check the hourly readings during the calm period and extrapolate that data.

If I started a test and during that time I got a heavy rain or snow, I’d simply report the results I got AND I would not be calling my results UNRELIABLE because your buyers are NOT gonna move out of the house in inclement weather.

In 28 yrs of radon testing the only time I’ve had anyone ask for a retest in situations like that were once in a while a SELLERS agent or SELLER. In that case I’m happy to retest AND tell my buyer to average the tests.

BUT there is a 2nd fee AND I tell my buyer they should have the seller or sellers agent pay for it since they wanted it.

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Thanks, Dan. These tests are supposed to be providing an estimate of the long-term average. By discarding a priori knowledge of outlier data (i.e. not testing during severe weather) I’d reason that doing so would give a better estimate of the long term mean.

If you were to report a high level found during severe weather, you’re effectively skewing the estimate higher than would be expected. Remember that the point of the test is to make a potentially expensive decision/demand during a real-estate transaction.

Part of being an analytical Radon professional is knowing how to interpret the results given the circumstances. If we could test every home for one year, anybody could do that provided they follow a few simple placement rules.

The problem is that the AARST training and protocols are, in my opinion, way out of date and unhelpful. What would be needed is further information on how to use ancillary data such as barometric pressure and precipitation amounts to make some sort of go/no-goo decision about the validity of the collected data.

That kind of correction is needed whenever such short samples are used as a proxy for a much larger sample time.

Todd Thuss

Integra Inspection Services, LLC

Huntsville, AL

The Radon test is a point in time inspection. Period. There is no prediction of future results, there is no compensation for weather, You measure for the allowed period and you report.

Anything else is severely overthinking the whole process. Those who would liken short term Radon tests to a statistical analysis are critically hampered by the SAMPLE SIZE. No amount of jugglng the numbers can change a small sample size. The margin of error is inversely proportional to the sample size. Small sample, large margin of error resulting in a low confidence in your results. There is simply no way to extrapolate long term test results from short term tests. Explain that to your customers! Any Radon mitigator worth his salt will retest after a short term fail. Doesn’t mean you should.

As an analogy consider well yield. You test and report a well yield at the time of testing. There is no way you can predict future rainfall or lack. Just report your measurement at the time of testing. If the results are unsatisfactory the well service company will retest.

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