FIELD: environment pollution control engineering. SUBSTANCE: method involves placing sample cleaned from aerosols and daughter products in a chamber having electrodes. Voltage is supplied to the electrodes so that the produced negative ions travel towards intermediate electrodes and the positive charged particles travel in the direction of internal electrodes. Electric pulsation number is recorded in the air caused by air ionization with alpha-particles. Their number counted within a given time interval is interpreted in terms of radon concentration in the air. The device has ionization chamber having internal, external and intermediate electrodes. The internal electrodes have negative potential Uint, the external ones have positive potential Uext and the intermediate ones have potential satisfying condition of UintUinterm≤Uext. EFFECT: high sensitivity of method and device. 5 cl, 1 dwg
