• There are three types of NSR permits that may apply to new emission sources or major modifications to existing.

The New Source Review (NSR) program makes sure that construction projects, whether new building or major modifications to existing facilities, do not worsen the air quality in a particular area. NSR permits describe what construction is allowed, emission limits, and even contains some operating requirements.

There are three types of NSR permits. A facility (i.e., source) may have to meet one or more of these permitting requirements.

• Prevention of Significant Deterioration (PSD). PSD permits are required for new major sources or major sources making a major modification in areas that meet National Ambient Air Quality Standards (NAAQS) attainment. No source or modification subject to PSD review may be constructed without a permit. PSD permits require installing pollution controls using the best available control technology (BACT). BACT is defined as an emission limit based on the maximum degree of reduction of each pollutant subjected to regulation under the Clean Air Act (CAA). BACT is done on a case-by-case basis, and considers energy, environmental, and economic impacts.
• Nonattainment NSR. These permits are required for new major sources or major sources making a major modification in areas that do not meet one or more of the NAAQS. Permits in nonattainment areas must meet the lowest achievable emission rate (LAER). In all cases, the BACT and LAER must be at least as strict as any existing New Source Performance Standards (NSPS) for the source.
• Minor source permits.

NSR permits are usually issued by states or local air pollution control agencies. The Environmental Protection Agency (EPA) issues NSR permits in some cases. State permitting requirements must be at least as stringent as those set by the federal government.

The EPA must approve a state’s NSR program in its State Implementation Plan (SIP).