As specified in Clause 7 of the Environmental Conservation Rules, all new industries and projects must apply for an Environmental Clearance certificate. Industries are classified according to their potential impact on the environment into four categories - Green, Orange - A, Orange - B, and Red. 

Green industries are automatically granted a clearance certificate. Orange categories must submit considerable further information and plans, and may be subject to field inspection. The highly polluting categories Orange-B and Red, must in addition conduct a detailed Environmental Impact Assessment and prepare environmental management plans satisfactory to the Department.
 
Details can be found in the Rules. Schedule 1 of the Rules provides the Category classification of most common industries.