Testing context

Two results disagree, and they used different devices

“The inspector got one number and our kit got a different one.”

Two measurements of the same house can differ for a long list of reasons that have nothing to do with either being wrong: different periods, different placements, different durations, different device types, different weather.

A disagreement is information about how variable this house is, which is genuinely useful. It is not by itself evidence that anyone made a mistake.

Why this matters

What it changes about the decision in front of you.

Indoor levels vary substantially over time in the same building, so two periods will frequently produce two figures.
Device types have different response characteristics, and a passive integrator and a continuous monitor are not measuring in quite the same way.

What it could influence

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

The gap between the two may reflect real variation rather than error, particularly across seasons.
Whichever figure a party prefers, the honest position is usually that both are real and describe different periods.

What this does not settle

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

Neither result is invalidated by the existence of the other, and the lower one is not automatically the correct one.
Disagreement does not indicate that a professional was careless — it is the expected behaviour of a variable quantity.
It does not establish which figure better represents the house annually, which is a different question again.

What a professional is likely to ask

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

The dates, durations, placements, and device types of both, side by side.
Whether closed conditions were stated for either, and by whom.
What decision the comparison is meant to inform, since that determines what would settle it.

What you can check yourself

Things you can establish today, without anyone visiting.

Both reports, laid next to each other, which usually explains more of the gap than people expect.
Whether the two tests were on the same level and in the same room.

What genuinely needs somebody on site

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

Whether the two placements would be expected to read differently in this building.

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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