Something about how the test was run is bothering you
Twelve things that commonly go wrong during a radon test, or commonly go unrecorded. Each one is written the same way: what it could influence, in which direction where that is knowable, and — the part most pages leave out — what your result still supports regardless.
That last part is not politeness. The predictable harm of a page like this is a homeowner who reads it, decides their measurement is worthless, and throws away both real information and the money that bought it. A concern about a test is almost never a reason to discard the result. It is a reason to know what the result can carry.
Device near a window or exterior door
“I have realised the kit was sitting on a windowsill, or right beside the back door.”
Perimeter air is influenced by the opening, not just by the room.
Tested in a kitchen or bathroom
“The kit went in the downstairs bathroom because that seemed like the lowest level.”
Those rooms describe themselves rather than the house.
The device was moved
“Someone tidied up and put the kit somewhere else partway through.”
One reading, two locations, no way to separate them.
Tested during severe weather
“There was a big storm halfway through the four days.”
Weather moves readings. It does not usually move them by a factor.
A whole-house or attic fan ran
“The attic fan was on for part of the test — nobody thought about it.”
Moving outdoor air through the house dilutes what you are trying to measure.
The test was shorter than intended
“We collected the kit early because we needed to post it.”
Duration is part of the result, not an inconvenience attached to it.
Only an unoccupied level was tested
“We tested the unfinished basement, but nobody goes down there.”
Guidance asks for the lowest level you live in, or reasonably could.
Windows were opened
“It was warm, and the windows were open on and off for a couple of days.”
The most common departure from protocol, and the easiest to describe.
The device was too low or too high
“It was on the floor in the corner, out of the way.”
Height is placement protocol, and it is easy to fix on a repeat.
Nobody recorded the conditions
“We ran the test but did not note anything about how.”
The result stands. Its defensibility is what suffers.
Comparing results from different devices
“The inspector got one number and our kit got a different one.”
Two numbers are only comparable when their conditions are.
Treating one result as permanent
“We tested when we moved in eight years ago and it was fine.”
A measurement describes a period. Buildings change; so do readings.
The other sections
Whatever you have noticed may not sit where you expect. If nothing here matches, one of these probably holds it.
- All three sections — the full index, with what each one covers.
- What we can and cannot determine online — the limits of everything on this platform, in one place.
When reading has taken you as far as it can
Describe your situation and we will tell you honestly whether we can route it to a provider in your area today, or whether we cannot.