Testing context

Only an unused level was tested

“We tested the unfinished basement, but nobody goes down there.”

Testing guidance asks for the lowest level currently occupied, or one that could reasonably become occupied. An unfinished basement usually qualifies under the second half of that, which is why it is the standard place.

It is a deliberately conservative benchmark: it makes houses comparable and tends to give the highest figure in the building. It is not a statement about where anybody breathes.

Why this matters

What it changes about the decision in front of you.

A basement figure is normally the highest in a house, so occupied floors above are commonly lower — sometimes considerably.
If the space could be finished later, the benchmark becomes directly relevant rather than theoretical.

What it could influence

Where the effect is likely to show, and in which direction where that is knowable.

The occupied floors are likely to read lower, but by an amount that varies with the building and cannot be estimated from a description.
A basement figure just above a threshold may correspond to occupied-floor figures below it, or may not.

What this does not settle

What still stands. Noticing a problem is not the same as losing the evidence.

The basement measurement is the standard benchmark and is exactly what a professional or a buyer will ask for. It is not the wrong test.
It establishes that soil gas is entering the building, which is the fact the whole conversation rests on.
It does not follow that upstairs is fine — nobody has measured upstairs.

What a professional is likely to ask

Worth having answers ready. None of these is a test you can fail.

Whether the basement is likely to be finished or occupied in future.
Whether anyone spends meaningful time down there now, including for laundry or work.
Whether an additional measurement on an occupied floor would change what the household decides.

What you can check yourself

Things you can establish today, without anyone visiting.

How the space is actually used, and whether that is likely to change.
Whether there is a floor above that would be straightforward to measure at the same time.

What genuinely needs somebody on site

Where this platform stops. These are not questions a website can answer about your house.

How air moves between the levels, which determines the relationship between the two figures.

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.

Review the testing context

When it is considered. When the conditions, placement, or duration of the test are unclear, which is the most common situation and the cheapest to resolve.

What it would establish. Whether the existing result is something to reason from, or something to repeat under conditions that can be described.

Discuss another test

When it is considered. When the prior result is disputed, the conditions cannot be reconstructed, or a longer observation period would answer the question being asked.

What it would establish. A second reading under conditions someone can describe, which is what makes two numbers comparable rather than merely different.

Request a professional assessment

When it is considered. When the building itself is part of the question — foundation type, an existing system, access, or an unusual layout.

What it would establish. What the building is doing, which no amount of information typed into a website can establish.

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.

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