Thai Iron and Steel Factory (TISF) expanded its existing plant to cater the higher demand in the downstream industries. Together with the new plant, the total capacity will exceed 100 tons/day, which requires EIA according to Thai law. In the EIA preparation, it was found that the most significant impact from the factory was air pollution caused by particulate matters (PM). The air pollution control system has been installed as the mitigation measure to minimize the dust released. Regular monitoring of indoor air quality and the air emission from the stack also was conducted to fulfill the compliance with Thai environmental laws and standards. Public participation was part of EIA process. TISF has also made efforts to initiate discussions and establish good relations with local communities and government officials, even since the development of the first plant began. The views and concerns of the communities have been noted and acted throughout preparation of the EIA through a community consultation process conducted by some scholars from the Faculty of Public Relation of Thammasat University. The response of local communities toward the project was positive, but they concerned more about the long-term management of its potential environmental impact. TISF ensured the regular monitoring as a mitigation measure would be carefully conducted. All process and results were recorded in a final report that forms part of the project documentation and was available in a form that can be understood by non-technical people from TISF for any interested party. The monitoring results showed the compliance of the project during both construction and operation phase. The measurement of air quality was regularly conducted every six months, and no single value exceeded Thai standard.