A compact tubular sensor based on NASICON (sodium super ionic conductor) and CaMg3(SiO3)(4) (Asbestos, acid washed A.R)-doped CdS sensing electrode was prepared for the detection of chlorine. The sensing properties strongly depended on the sintered temperature of the sensing electrode materials. The sensor using CaMg3(SiO3)(4)-doped CdS sintered at 600 degrees C gave excellent sensing properties to 1-10 ppm chlorine in air at 100-250 degrees C. The sensitivity (slope) was 392 mV/decade at 200 degrees C. And it showed a good selectivity to Cl-2 against H2S, SO2, NO2, NH3, CH4 and CO. Also it had speedy response kinetics to chlorine, the 90% response or 90% recovery time to 5 ppm chlorine was 20 s or 37 s, respectively. The phase compositions and grain size of NASICON and CaMg3(SiO3)(4)-doped CdS were examined by means of X-ray diffraction (XRD). On the basis of XPS analysis for Cl-2-absorbed sensing electrode, a sensing mechanism involved the mixed potential at the sensing electrode was proposed. (C) 2008 Elsevier B.V. All rights reserved.