RE: I-125 Gas Calibration Source

["Mike Bohan" <mike.bohan@yale.edu>]

        Reply to:   RE: I-125 Gas Calibration Source

Carol & RadSafe,

What type of filter are you using?  We used to use activated charcoal paper disks in our hood monitors.  The way we calibrated them, is to stack two filters on the initial use of the hood and compare the absorption ratios between the first and second filters.  This gives you the first two terms in an infinite series that you can use to calculate filter efficiency.  

I think you would have a hard time finding a gaseous I-125 calibration source and it probably will not be in the same chemical form as the byproducts coming off the reactions in your hood anyway.  Additionally, how can you be sure that the entire amount gets to the filter.  You would have to assay all prefilter components, which I would imagine could introduce a number of difficulties and uncertainties into the final result. 

Hope this helps,

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Michael J. Bohan, RSO   |  e-mail: mike.bohan@yale.edu
Yale-New Haven Hospital |    Tele: (203) 688-2950
Radiological Physics    |     FAX: (203) 737-4252
20 York St. - WWW 204   |    As usual, everything I say may be plausibly
New Haven, CT    06504  |    denied at my employer's convenience ...
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--------------------------------------
Date: 05/05/1998 4:00 PM
To: Mike Bohan
From: radsafe@romulus.ehs.uiuc.edu
>  
> 
> We have installed a 125-I air monitor in our iodination fume hood
> stack.
> We would like to calibrate this in place using 125-I gast to determine
> the system's efficiency. Does anyone know where to obtain 0.1 uCi of
> 125-I gas?
> 
> Carol Lentz
> 
	  carol.lentz@wl.com