The purpose of this study is to investigate the method of trace gas technique by G.C and the effects of the type of blouse on ventilation. The experimental system employed a trace gas technique in which ventilation was monitored to determine oxigen exchange rate. The experimental variables were tested with three types of blouse depending on the sizes of neckline, armhole and waist line. Exercise conditions include standing and walking position. The results and discussion forcused on the construct validity of the apparatus/testing protocol. the effect of experimental variables on ventilation was also discussed.