A passive diffusion method for the determination of radon concentration has
been optimised and calibrated. The device consists of a scintillation vial
containing activated charcoal, a diffusion barrier and a desiccant agent.
The response to diverse atmospheric humidity and variable exposure interval
s was studied. The result is a detector independent of atmospheric humidity
till 7 days of exposure. The method was compared with electret detectors (
US EPA) with very satisfactory results. The advantages of this method are i
ts simplicity, low cost, low detection limit, the total automatization of t
he measurement and its total independence of humidity to measure in a wide
range of radon concentrations.