Some entry efficiencies for sharp-edged samplers in calm air

The method is an improvement of that of OGDEN (1974), and has the following advantages over other methods: the measurements do not require special samples, but can be made on ordinary airborne dust samples; the long sampling time (> 2½h) is more suitable for estimating average exposure than the conventional short sample; radon and thoron working levels are both obtained; and the method is very sensitive (0.001 WL is easily measured). Side-by-side comparisons show good agreement with other methods.