The detection of the interface between turbulent and nonturbulent zones in slightly heated turbulent shear flows on the basis of a temperature signal is discussed. Two detection parameters, a threshold level or gate &dgr;&thgr;gand a hold time &tgr;h, are used. A complete description of the detection process and of the procedure used to select nominal values for the detection param eters is presented. It is shown that the detection process is credible in the sense that the statistics of the intermittency function are nearly independent of the values of the detection parameters. Comparison of the intermittency function statistics with previous results is made.