[en] Self (quenching streamer) mode, a new development of gas detector. The gas filled detector operating in the SQS mode region has been widely used for nuclear radiation detection. The charge amplification process, the growth of electron avalanche mechanism and the SQS mechanism in a gas detector are reviewed briefly in this paper. The gas mixture composition, gas pressure and anode diameter of a gas play an important role in the streamer formation. (author). 9 refs.; 6 figs