The test ran through severe weather
“There was a big storm halfway through the four days.”
Barometric pressure and wind change the pressure relationship between a building and the soil beneath it, which is the mechanism that drives soil gas indoors. Guidance advises against testing through severe weather for that reason.
The effect is real and it is also frequently overstated by people hoping a result will go away. A storm is a reason to note the context, not a reason to assume the number is wrong.
Why this matters
What it changes about the decision in front of you.
- Falling barometric pressure tends to increase soil-gas entry, so a storm period can push a short test upward.
- High wind changes how a building leaks, which affects both entry and dilution in ways that are not uniform across a house.
What it could influence
Where the effect is likely to show, and in which direction where that is knowable.
- A short test that included a significant pressure swing may sit higher than the same house would read over a settled week.
- The shorter the test, the larger the proportion of it the weather event represents, so a two-day test is affected more than a seven-day one.
What this does not settle
What still stands. Noticing a problem is not the same as losing the evidence.
- Weather does not manufacture soil gas. A high reading during a storm still indicates that the building draws soil gas when conditions favour it, which they will again.
- The result remains a valid data point about the house under a describable condition, and describable conditions are what make results comparable.
- It does not mean a calm-weather test would come back below any particular figure.
What a professional is likely to ask
Worth having answers ready. None of these is a test you can fail.
- What the weather actually did and when, relative to the test period.
- The test duration, because that determines how much of the measurement the event covers.
- Whether a longer-duration measurement is practical, since duration is the usual answer to weather.
What you can check yourself
Things you can establish today, without anyone visiting.
- The dates of the test against the dates of the weather, both of which are recoverable.
- Whether the device produces an hourly record that would show the swing.
What genuinely needs somebody on site
Where this platform stops. These are not questions a website can answer about your house.
- How this particular building responds to a pressure change, which varies with construction and cannot be inferred.
Categories a next step could fall into
Unordered, and none of them is a recommendation. Which applies depends on things this page does not know about your situation.
Related reading
- Weather effects — Weather genuinely moves indoor radon — but it explains variation around a number, not a number well above the action level.
- False positives — Most disputed results are not false — they are invalid, mismeasured, or comparing two different things.
Sources
- U.S. EPA — A Citizen’s Guide to Radon
- U.S. EPA — Radon
When you are ready to talk to somebody
Tell us about your home and what you are trying to work out. We will tell you honestly whether we can route it to a provider in your area today.