The majority of radon measurements in the built environment are made over sub-year periods and are then generally seasonally corrected (i.e. scaled by an appropriate seasonal correction factor (SCF)) to estimate the annual average radon concentration. SCFs are statistically derived and assume an underlying annual cycle, reflecting the widely observed seasonal variation in indoor radon concentrations. In the UK, Public Health England has pioneered the calculation and use of a national SCF set using an annual sinusoidal model for variations in radon concentration and averaging across the entire country.

To test the validity of that model, a 4 year...