Panasonic PT-DZ12000U Operating Instructions Manual page 124

B. Flow Through
Flow through chambers generally are combined with some
detection method. Applications include sampling for
radioactive substances, both gas and particulate, and
sampling for toxic substances.
When sampling for radioactive substances the typical flow
through chamber is a version of the air ionization chamber
used for the detection of gamma detection. The actual
gamma radiation background must be subtracted from the
total signal level to determine the actual concentration of the
radioactive substance.
Sampling for toxic substances using a flow through
chamber generally requires an electrochemical detection
method. Some flow through detectors for toxic substances
have the capability of detecting more than one type of toxic
substance.
Sampling for oxygen deficient atmospheres is another
application for flow through chambers.
C. Grab
The basic technique in grab sampling is to cause the air to
be sampled to flow through or into the collection container.
This can be accomplished by using a pump and when the
container is sufficiently purged simply close the outlet and
inlet valves on the container.
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