Radiation Safety Toolkit v2.0
Radon Gas Measurement by
Refer to either the VS472 User
Manual for the
Take a 5 minute
background count on a small Aluminum Lucas cell (serial number starts with
"A"). This count should be below 50.
Collect a sample as
described in the Grab Sampling Setup section of one of the above user's manuals. Alternatively
another pump can be used, rather than the radon sniffer's internal pump. Make sure
you use an inlet filter.
Wait between 1 and 4
Count the cell using a 5 minute
Enter the gross count,
background count and time between sampling and counting in the form below
and hit CALCULATE NOW. (Accept all other default values.) The radon gas
concentration will be displayed. As a rule of thumb, 1 count in 5 minutes
corresponds to ~ 10 Bq/m3 or 0.25 pCi/L. Longer count times can
be used to increase accuracy.
Pump clean air through
the cell for about 10 minutes using the radon sniffer's internal pump or a different
pump. (Some people prefer dry nitrogen, to ensure extremely low levels of
radon in the cell.)
Wait at least 3 hours
(preferably overnight) before taking another background reading and re-using
the cell. (This allows the radon progeny, attached to the walls of the cell
If the background
count is high, you may have to purge again and/or wait longer.
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