The simultaneous radon & thoron monitoring method based on the difference of the half-life between radon and thoron,the thoron monitoring method with absorber based on the difference of the energy of α particles emitting from radon,thoron and their progenies,and the sensitive thoron monitoring method with electret based on the charged characteristics of thoron daughters are developed.The simultaneous method can be used to measure radon and thoron concentrations simultaneously;the thoron monitoring method with absorber can measure not only thor...