APR-1140-1 

San Joaquin Valley 

Unified Air Pollution Control District 

Interim New Source Review Requirements for PM2.5

 Approved By: <signed> Date: 10/27/09 

 David Warner 

 Director of Permit Services 

PURPOSE 

The purpose of this policy is to outline interim Federal New Source Review (NSR) 

requirements for PM2.5 for new major sources and federal major modifications. These 

requirements are specified in 40 CFR Part 51.165 and the EPA Emission Offset 

Interpretive Ruling (Part 51 - Appendix S) and are effective as of July 15, 2008. 

The Appendix S requirements for PM2.5 will apply until Rule 2201 is amended to 

incorporate provisions for PM2.5, i.e. no later than July 15, 2011. 

These new PM2.5 requirements are in addition to the existing requirements in Rule 2201 

to quantify PM10 emissions. 

APPLICABILITY 

The Appendix S requirements are applicable to new major PM2.5 sources and federal 

major modifications of PM2.5 and its precursors. The thresholds are as follows: 

PM2.5 major source 

threshold 

100 ton/year 

PM2.5 federal major 

modification threshold 

10 ton/year 

The federal major modification calculation procedure is contained in the latest version 

of 40 CFR 51.165 (See 51.165 (a)(2)(ii)(B) through (D) and (F)). 

Please note that the above thresholds are different than the PM10 major source 

threshold of 70 ton/year and major modification threshold of 15 ton/year. 

Due to lack of appropriate test methods, quantification of PM2.5 emissions does not 

include the condensable fraction of PM2.5 at this time. Only the filterable portion of PM2.5

is required to be used to determine major source and federal major modification 
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applicability. By January 1, 2011 EPA will establish appropriate test methods for the 

condensable fraction of PM2.5. After that date (or earlier if EPA specifies), all 

applicability determinations must use both the filterable and condensable fractions of 

PM2.5. 

SO2 is stipulated as a PM2.5 precursor in Appendix S. In Appendix S, the SO2 major 

source threshold is 100 ton/year, and the major modification threshold is 40 ton/year. 

As the Rule 2201 SO2 major source thresholds (70 ton/year) and major modification 

threshold (40 ton/year) are equal to or lower than lower than those in Appendix S, Rule 

2201 is no less stringent than Appendix S. As such SO2 emissions will be omitted from 

the Appendix S compliance determination. 

NOx is not stipulated as a PM2.5 precursor in Appendix S. However by January 11, 

2011 the District must establish if NOx is a precursor to PM2.5. At that time, the District 

will have to either establish that NOx is not a precursor to PM2.5 or establish a 

significance threshold for NOx as a precursor to PM2.5. Therefore NOx will not be 

regulated as a PM2.5 precursor until Rule 2201 is amended. 

 

Appendix S requirements PM2.5 apply to Authorities to Construct issued after July 15, 

2008. 

APPENDIX S REQUIREMENTS FOR PM2.5 

Appendix S provides implementation guidelines for the federal non-attainment NSR 

regulations in 40 CFR 51.165. For the purposes of this policy, Appendix S only applies 

to new major sources for PM2.5 (100 ton/year) and federal major modifications for PM2.5

(10 ton/year). 

For purposes of Appendix S, PM2.5 only includes the filterable fraction. It does not 

include condensables. 

Appendix S requires that offsets for PM2.5 emission increases be provided for new 

major sources and federal major modifications. Such offsets must be surplus of 

Federal requirements at the time of ATC issuance for the emission increase, i.e. 

surplus at the time of use. Please note that this is a major departure from the District’s 

current offset system (surplus at the time of ERC issuance). 

Appendix S specifies that the distance offset ratio shall be at least 1:1. The distance 

offset ratio for using PM2.5 emission reductions to offset PM2.5 emission increases will 

be the same as the distance offset ratio specified in Rule 2201 Table 4-2, i.e. ranging 

from 1:1 to 1.5:1 depending on the distance between the emission reduction and the 

emission increase. 

In the Appendix S PM2.5 implementation Federal Register notice EPA established a preapproved interpollutant offset ratio of SOx/PM2.5 = 40:1 for anywhere in the country. 
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Based on preliminary guidance from EPA, use of any other interpollutant offset ratios 

for PM2.5 are not allowed until Rule 2201 is amended (and approved by EPA) to include 

provisions for PM2.5, including the specification of interpollutant ratios in for PM2.5. 

IMPLEMENTATION POLICY 

Any ATCs issued after July 15, 2008 must comply with the requirements of Appendix S, 

as they apply to PM2.5 and PM2.5 precursors (SOx). 

Existing stationary sources

The procedure below is intended to be a streamlined approach in determining if a 

project at an existing stationary source is subject to Appendix S, i.e. is the project a 

federal major modification at a major PM2.5 source. 

Step 1 If the stationary source is not major for PM10, the project is not subject to 

Appendix S. No further analysis is necessary. If the stationary source is 

major for PM10, go to step 2. 

Step 2 If the stationary source is major for PM10, calculate the emission increase 

in filterable PM2.5 emissions pursuant to the requirements of 40 CFR 

51.165. In general, for new emission units the emission increase is equal 

to the potential to emit. For existing emission units the emission increase 

is the difference between the potential to emit or the projected actual 

emissions (if the applicant provides a sufficient data to establish projected 

actual emissions) and actual emissions. 

 PM2.5 emissions calculations shall be based on emission factors for 

filterable PM2.5 from manufacturer’s information, AP42, or best 

engineering judgment. Please note that some chapters in AP42 provide 

documentation on the filterable fraction and size range of particulate 

matter emissions from a particular process. AP42 Appendix B includes 

particulate matter size distributions for selected sources and generalized 

size distributions. 

Step 3 If the filterable PM2.5 emission increase calculated pursuant to 40 CFR 

51.165 is greater than 10 ton/year, the project may be a federal major 

modification for PM2.5. 

To definitively determine if the project is a federal major modification for 

PM2.5, determine if the stationary source is major for PM2.5. Alternatively, 

the stationary source may stipulate that the facility is a major source for 

PM2.5. 
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Step 4 If the facility has not stipulated that the stationary source is major for 

PM2.5, pre-project stationary source potential to emit (SSPE1) for PM2.5

must be calculated. Remember, PM2.5 emissions only include the 

filterable fraction. The condensable fraction is not quantified. 

Step 5 If the stationary source PM2.5 potential to emit is less than 100 ton/year, 

the project is not subject to Appendix S. No further review is necessary. 

 If the stationary source PM2.5 potential to emit is equal to or greater than 

100 ton/year, and the increase in emissions from the project is greater 

than 10 tons/year, the project is subject to Appendix S. 

Step 6 BACT is required for PM2.5. A BACT analysis for PM2.5 must be 

performed. In the BACT analysis for PM2.5, existing control technologies 

for PM10 should be considered if they are effective at controlling PM2.5. 

PM2.5 offsets must be surplus of federal requirements at the time of ATC 

issuance. The distance offset ratio for using PM2.5 emission reductions to 

offset PM2.5 emission increases will be the same as the distance offset 

ratio specified in Rule 2201 Table 4-2, i.e. ranging from 1:1 to 1.5:1 

depending on the distance between the emission reduction and the 

emission increase. 

The interpollutant offset ratio pre-approved by EPA is SOx/PM2.5 = 40:1. 

 An air quality impact analysis, alternative siting analysis, and a state-wide 

compliance certification is required. 

New PM2.5 stationary sources

Step 1 Calculate the PM2.5 SSPE2 for the new stationary source. If the PM2.5

SSPE2 is less than 100 ton/year, the stationary source is not major for 

PM2.5 and is therefore not subject to Appendix S. No further analysis is 

necessary. 

If the stationary source is major for PM2.5, go to Step 2. 

Step 2 BACT is required for PM2.5. A BACT analysis for PM2.5 must be 

performed. In the BACT analysis for PM2.5, existing control technologies 

for PM10 should be considered if they are effective at controlling PM2.5. 

PM2.5 offsets must be surplus of federal requirements at the time of ATC 

issuance. The distance offset ratio for using PM2.5 emission reductions to 

offset PM2.5 emission increases will be the same as the distance offset 

ratio specified in Rule 2201 Table 4-2, i.e. ranging from 1:1 to 1.5:1 
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depending on the distance between the emission reduction and the 

emission increase. 

The interpollutant offset ratio pre-approved by EPA is SOx/PM2.5 = 40:1. 

 An air quality impact analysis, alternative siting analysis, and a state-wide 

compliance certification is required.