I have a modified vacuum hose I use for sub slab diagnostics. It has T with a ball valve to bypass the suction. I use it to dial down the pressure to better simulate a fan's suction level. [img]http://c:\users\jim\googledrive\radonguys\floorplans\img_2456.jpg[/img]

Semantics I think. A reading is what is given by the device. A test is a defined protocol, of which in radon measurement, 48 hrs is the min. defined by the standards. Certainly the wording, which I didn't review directly, on the device website or documentation may be misleading.

Thanks Bill. I attended that session but did not recall that information until I saw the slide.

Bill - your data is extremely helpful. Any consideration to measuring noise curves also as noise is a concern for attic and even outside installs sometimes. Vibration is another but not sure you could do little more than provide subjective reporting.
Jim