Re: airfilters and radon daughters

[SAFarberMSPH@CS.COM]

In a message dated 11/29/01 11:00:19 AM Pacific Standard Time, blc+@PITT.EDU writes:



> If there is a problem with high exposures, people can stay
>
> away from the filter for an hour after the air flow is cut off; that will
>
> allow most of the radon daughters to decay away.

Radsafe:

The short-lived radon daughters collected on any air filter have an approximate half life of about 30 minutes. An hour would reduce activity by a factor of about 4 and  that would meet the comment by Dr. Cohen about "most" [ie: about 75%] of radon daughter activity having decayed away. Most but not all.


I recall in rounting REMP programs in counting environmental particulate air sampling filters for long-lived beta activity, the EPA recommended that filters be counted after 24 hours of daughter product decay, a time when essentially all the particulate radon daughters from the original sampling would have decayed away allowing only long-lived beta activity to be counted.


Stewart Farber

email: SAFarberMSPH@cs.com

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