English Abstract Automated monitors for the determination of airborne
radioactivity are widely in use as 'early warning' systems for nuclear
emergencies, but seldom applied in quantitative studies to the appearance of
natural radioactivity (especially radon and short-lived decay-products).
This report describes how a specific type of airborne gross-alpha/beta
monitor (FAG FHT59S), which is used by the Dutch National Radioactivity
Monitoring Network (NRM) for the surveillance of the inhalation pathway, can
be applied for this purpose. The main focus is on the performance of the
applied algorithm which recalculates actual air activity concentrations from
primary measurements, especially for circumstances contradicting assumptions
made by the manufacturer. Furthermore, a complete uncertainty analysis has
been carried out. As a result, a formula has been derived which converts,
within a reasonable degree of uncertainty, the monitor recordings to the
equilibrium-equivalent decay-product concentration (EEDC) of Rn-222.
NRM-data of Rn-222 (progeny) obtained in this way agree with results of
previous radon surveys carried out in the Netherlands.