In this work, effective countermeasures were studied against chemical accident by studying how to find out source point and take measures directly. Through this study, emergency response system will be modified by applying dispersion modelling, which includes; (1) most of hazardous materials emitted to atmosphere or dispersed in the form of fume have high potentila of chemical accident, (2) emergency response system were suggested through countermeasures against dispersion to atmospheric conditions. (3) It is necessary for the government to develop various type of protection equipment to supply.