Re: Puzzler: How Does Humidity Affect Counting Efficiency?

[Gv1@AOL.COM]

I agree with the issue with barometric pressure being the primary variable in 

changes in radon concentrations.  Much data collected in college.  I also 

remember there was a bit of lag on the increase in radon concentrations following 

the barometric pressure.  Pressures above a slab can equalize quickly with 

the outside and drop leaving a higher pressure beneath the slab.  This delta P 

above and below the slab provides the motive for transport.  Concentrations 

will continue to increase as the gas diffuses out of the soil until delta P above 

and below the slab go to 0.



We recently went through an incident with high humidity conditions and a loss 

of HVAC with plastic scintillator personnel monitors.  Humidity caused some 

of the HV/scaler cards to increase counts and some of the counts went down on 

others.  Run a blow drier directly on such a component and look for count rate 

changes.  We found direct and immediate changes with hot air applied to remove 

moisture to such components.  We installed a couple of portable spot coolers 

in the area to pull moisture out of the air.



Glen Vickers