32 | PRM-7000 / 8000 / 9000 Users Guide
4. Perform a timed measurement of at least 60 minutes and note any
amount of radiation measured above that of the established back-
ground baseline of step 2 above.
5. A second alternative is to evaporate or boil the substance. The remain-
ing concentrate can then be measured.
6. When measuring water and similar liquids that are available in relative
abundance, such as pond or rain water, it is recommended to augment
this procedure by fi ltering a large amount of the liquid using a coffee
fi lter or other fi lter. After fi ltration, measure the fi lter using “14.3 Mea-
suring Objects”
NOTE: For those interested in testing for radioactivity of well-water, a convenient
location for testing is any water fi lter that may be in line with the water supply. When
changing fi lters, simply measure the fi lter using the procedure (See “14.3 Measuring
Objects”)
14.7 Measuring Air
To measure contamination in air using the PRM Instrument, it is generally necessary to
measure the contents of a fi lter that has been in use for a reasonable amount of time to
fi lter the air of interest. Examples include whole-house heating and cooling fi lters, HEPA
Filters and automobile cabin fi lters. Particles concentrate in the fi lter elements and if any
radioactive substances will likely be in the concentrate as well. It is a good practice to
measure these fi lters periodically if there are any concerns about radiation.
To measure the fi lter, follow the procedure “14.3 Measuring Objects”with the addition of
the following guidelines:
1. Be careful not to allow any of the dust from the fi lter to enter the
PRM Instrument. This could contaminate the instrument.
2. Orient the fi lter with the surface area of the fi lter in the vertical position
and rest the PRM Instrument on a stack of books, or other appropriate
shim that provides a stable surface for moving the PRM Instrument as
close to the fi lter as possible, without touching the fi lter.
NOTE: Placing a piece of thin plastic in between the fi lter and the PRM Instrument
will block the detection of alpha particles, but this arrangement will continue to enable
the detection of other types of ionizing radiation.
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