Casella CEL Sampling heads for personal dust sampling - Manual (Page 6)

2. FILTERS
There are two commonly used types of filter for airborne dust sampling; glass
fibre (GFA) and membrane filters (MCE). However, many other types of filter
also exist.
2.1 Glass Fibre (GFA)
It is likely that most gravimetric dust sampling will be done with GFA filters.
2.2 Membrane (MCE)
Usually made from a polymer material and available in a variety of pore sizes.
For more specific information about filters and their application please contact
the Casella CEL sales office which will be able to advise you.
Caution !
All filters are delicate, especially GFA and must always be
handled with flat tipped tweezers, never by hand.
It is important to remember to remove the backing paper
from a membrane type filter before sampling. The
backing is usually blue.
Several sampling heads incorporate a filter cassette system that holds the
filter. The aim of the cassette is to reduce filter handling, and thus make
loading the sampling head quicker and easier. One advantage is to reduce
potential under-reading.
The entire cassette is weighed, including filter and particulate, not
just the particulate on the filter paper. Under-reading occurs when particulate
is deposited on the inner surfaces of the sampling head, and not included in
the final sample.
The two halves of the cassette snap together to hold the filter in
place. Ensure the cassette is seated properly in the sampling head, to avoid
leaks.
Filters
Page 6 of 24
SAMPLING HEADS AND ACCESSORIES
Users Guide