Re: Removable Contamination Surveys

[ARDeAngelo@AOL.COM]

Over the years, I have heard the following rationales for the 100 cm2  (16 

in2) area of a smear:



 - Conveniently sized area that roughly matches the area of the palm of a 

hand, or the area covered by a knee on the floor.



 - Limited to that size because a dry wipe would either start to 

degrade/wear-through with a larger area and/or have a significantly reduced 

collection efficiency after loading up with dust.



 - Approximately the sensitive area of a surface measurement with a standard 

sized "pancake" GM probe ... so the smear was comparable to a direct 

measurement of the same surface.



Any or none of the above could be right.   Bottomline is that it is the 

customary measurement ... to deviate from it would make intercomparison of 

past and present measurements difficult.



As far as references, others have already mentioned excellent sources where 

the standard area has been enshrined ... if not justified.



Tony DeAngelo

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