Re: querry: back-half of particulate samplers

[Kaltofen@aol.com]

The back half of PM samplers should be completely blank, meaning free of
particulates.  It is for quality control purposes only.  If any particulate is
in the back half, the capacity of the tube was exceeded and the sample is
invalid.  It should be redone at a lower rate.  If resampling is not possible,
the sample represents a minimum concentration, and may actually be higher than
stated. 

A better estimate would be to include the back half to give a somewat higher
and more correct minum value.  Of course, since there are no more halves left
to check, there is no way to see if the back half has also exceeded its
capacity.  Thus there is still the possiblility that the true concentration is
even higher.

To have a detectable back half concentration, and not add it in, is a
deliberate underestimation.

Marco Kaltofen, P.E.
http://members.aol.com/kaltofen/menu.html