Panasonic PT-DZ12000U Operating Instructions Manual page 125

Another technique used is to fill the sampling container
with water and when the inlet and outlet valves are opened
the water flowing out draws the air to be sampled into the
container.
Sampling containers can be evacuated using a vacuum
pump before sampling the air and when the sample needs to
be collected the technician simply opens the inlet valve on the
sampling container.
D. Filtration
Filtration is the most widely used method for collecting
samples of aerosols.
The methods and equipment range from high volume
samplers (up to about 40 cfm) for environmental or short-term
workplace sampling, to low-volume lapel samplers (1 lpm or
less) for collecting aerosols in the breathing zone of individual
workers.
Low-pressure-drop, cellulose filters are commonly used,
and samples can be easily reduced to ash or dissolved for
analysis without the filter material interferring with the
analysis.
Concerns for penetration of particles into the filter matrix
are a function of the type of filter and the filter analysis
method. Membrane filters with their superior front-surface
collecting characteristics are preferred over fiber-type filters
when alpha particle spectroscopy is applied. Shielding by the
filter media is seldom a concern for detection of gamma
particulate radiation.