Korea has adopted Environmental Impact Assessment (hereafter “EIA”) system for more than 3 decades. There are 74 big projects subject to EIA according to (Environmental Impact Assessment Law (No. 10892). For thermal power plant of which output is more than 10 MW, EIA must be done by proponents. To assess impact on atmospheric environment, proponents utilize air dispersion models and to minimize the adverse impact on air quality, state-of-the-art add-on control technology is applied.