Re: Particulate Air Sampling

[Wes Van Pelt <vanpelt@ios.com>]

Larry_R_Sanders_at_~BMI4@battelle.org wrote:
> 
> 
>      I am currently faced with a need to perform air sampling for 0.1 - 0.3
>      micron particulate radionuclides. I have information on how to perform
>      this for 0.75 micron particles and higher. Below this range I have no
>      information. I would appreciate any input I receive.
> 
>      Larry R. Sanders
>      larry_r_sanders_at_~bmi4@battelle.org

Larry and Fellow Radsafers,

Particles at around 0.3 um diameter are generally the most difficult to
filter.  They are too large to get much diffusional deposition by
Brownian motion, and too small for much inertial deposition by impaction
on the filter fibers.  (This is why absolute filters are tested at 0.3
um particle diameter!)

You can use a particulate filter (glass fiber or membrane) which has
specs giving decent TRAPPING EFFICIENCY at 0.3 um.  Also, you need to
check the linear air flow velocity thru your filter versus the
manufacturer's specifications.

If you are going to do alpha counting you need to determine the self
absorption due to where the particulate deposits in the filter .... some
filters deposit on the surface (membrane) and some deposit throughout
the mass of the filter (paper, glass fiber).

cheers, Wes.

-- 
Wesley R. Van Pelt, Ph.D., CIH, CHP                   KF2LG
President, Van Pelt Assoc., Inc.            vanpelt@ios.com
Consulting in radiological health and safety.
"TIME, its what keeps everything from happening at once."