Re: airfilters and radon daughters - Thoron vs. radon

[SAFarberMSPH@CS.COM]

In a message dated 11/29/01 3:14:06 PM Pacific Standard Time, idias@interchange.ubc.ca writes:


>  
>
> 24 hours of decay is fine if the Ra-220 concentration is low, but the thoron progeny are longer lived that the radon progeny.
>
>  

Radsafe:


Thoron [Rn-220] has a half life of only 56  seconds vs. Rn-222 at 3.8 days. Thoron airborne levels are accordingly usually quite negligible [often thoron does not even escape to any degree from the soil, or thorium bearing rock,  or building materials due to its very short half life vs. Rn-222] so the thoron progeny in air would almost always be very low as well.


Stewart Farber

email: SAFarberMSPH@cs.com