Some Lucas cells ( see earlier article) work by drawing the air through with
a pump
and monitoring for Radon (or Thoron) on a continuous basis over a long
period of time.
See:

The Pylon AB-5 is really a great setup, but hardly practical to take on,
say, a cave tour.

My Pylon set is pretty complete, including an outboard PMT tube and adaptors
to run the Lucas Cell
away from the main unit if desired. Normally the Lucas Cell fits right on to
the front of the AB-5 and is read by an internal PMT.

The external PMT/Lucas Cell adaptor can also be read on any other meter or
scaler. With this in mind, a handy pocket sized 125 ml Lucas Cell was rigged
up to the external PMT by providing a cardboard spacer to make it fit the
Pylon fitting.
See PHOTOS/Lucas Cell file.

As mentioned the Pylon Lucas Cells use a flow through, 2 port system without
conventional valves. For this purpose a single port Lucas Cell was chosen
with a valve. In use the Lucas Cell evacuated of air using a MITYVAC hand
vacuum pump, then the valve closed. Tests indicate the vacuum will remain
charged for months at a time.
Approx 25 inches of mercury vacuum can easily be pulled with this <$20 hand
pump.

After the Lucas Cell is ready, bring one or two along to the sample site.
Only the cells are needed- not the rest of the apparatus during collecting.
Once on scene of the test, simply open the valve and the ambient air will be
drawn into the Lucas Cell for evaluation back at the Mobile or Home Lab.

Best to clean the Radon daughters from a used cell by evacuating and
releasing the vacuum a few time in clean air.

Have fun

Geo