Permits are issued for stationary sources of air contaminants. The issued permits specify limits on the quantity of air contaminants emitted and requirements for construction and operation of regulated of air contaminant sources. Permit conditions also specify the emission testing, monitoring, record-keeping and reporting requirements applicable to each source. These requirements are the primary means for evaluating and demonstrating compliance with the emission limits established in each permit.

There are a variety of permit options available depending on the type of source, existing air quality where a source is or will be operated, operational flexibility needed by the source and whether additional voluntary restrictions are requested to be included in the permit. More than one of these factors can apply to the permitting process for a given source. In general, think of permitting in terms of “permitting programs” and “types of permits” based on the type of facility and when sources are installed and operated as described below. When the source was installed or will be installed also affects the type of permits that must be issued for the source. Finally, several types of exemptions have been developed over the years that range from not being subject to regulation (de minimis operations) to permit-by-rule exemptions (i.e., there are restrictions and obligations that must be complied with, but no issued permit is required).