Radon and thoron working levels from ordinary industrial-hygiene dust samples

The method is an improvement of that of Ogden (Ogden, T.L., Ann. Occup. Hyg., 17, 1974, 23-34), 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 (> 2 1/2 h) 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 comparisions show good agreement with other methods. (author)