N.Y. Comp. Codes R. & Regs. tit. 6, § 231-12.2 – Modeling analysis methodologies.

(a) The ambient impact analysis must follow the procedures in the applicable guidelines at 40 CFR part 51, appendix W: Guideline on Air Quality Models of the EPA and a modeling protocol which has been approved by the department. Emissions of PM-10 and PM-2.5 used in a modeling analysis for this Part must include both the filterable and condensable fractions (see definitions of PM-10 and PM-2.5 in Part 200 of this Title).
(b) Where an air quality model specified in appendix W of 40 CFR part 51 is deemed inappropriate, the model may be modified or another model substituted. Such a modification or substitution of a model may be made on a case by case basis or, where appropriate, on a generic basis for a specific program. Written approval from the department must be obtained for any modification or substitution. In addition, use of a modified or substituted model shall be subject to public notice and opportunity for public comment, with the determination of a complete permit application, in accordance with Parts 201 and 621 of this Title.

(c) For the purposes of Subparts 231-7 and 231-8 of this Part, the owner or operator of the proposed new or modified facility must demonstrate that allowable emission increases from the proposed facility or modification, in conjunction with all other applicable emissions increases or reductions (including secondary emissions) would not, at a minimum, cause or contribute to air pollution in violation of:

(1) any national ambient air quality standard in any air quality control region;
(2) quantified air quality related values (AQRVs) including visibility for the applicable Federal class I areas; and

(3) any applicable maximum allowable PSD increment increase over the baseline concentration in any area, as defined in the following table: For any period other than an annual period, the applicable maximum allowable increase may be exceeded during one such period per year at any one location.

Contaminant	Maximum allowable increase (micrograms per cubic meter)
Federal Class I
Particulate matter:
PM-10, annual arithmetic mean	4
PM-10, 24-hr maximum	8
PM-2.5, annual arithmetic mean	1
PM-2.5, 24 hour maximum	2
Sulfur dioxide:
Annual arithmetic mean	2
24-hr maximum	5
3-hr maximum	25
Nitrogen dioxide:
Annual arithmetic mean	2.5
Class II
Particulate matter:
PM-10, annual arithmetic mean	17
PM-10, 24-hr maximum	30
PM-2.5, annual arithmetic mean	4
PM-2.5, 24 hour maximum	9
Sulfur dioxide:
Annual arithmetic mean	20
24-hr maximum	91
3-hr maximum	512
Nitrogen dioxide:
Annual arithmetic mean	25
Class III
Particulate matter:
PM-10, annual arithmetic mean	34
PM-10, 24-hr maximum	60
PM-2.5, annual arithmetic mean	8
PM-2.5, 24 hour maximum	18
Sulfur dioxide:
Annual arithmetic mean	40
24-hr maximum	182
3-hr maximum	700
Nitrogen dioxide:
Annual arithmetic mean	50

(d) The emission rates for any existing emission sources to be used for the analysis of increment increases in paragraph (c)(3) of this section can be based on representative actual emissions instead of the allowable emission rates, provided the maximum actual rates under representative normal operations are used for short term increments. Any increment expansions analysis for the purposes of paragraph (c)(3) of this section must use representative actual short term and annual emissions instead of the allowable emissions.
(e) For the purposes of Subparts 231-5 and 231-6 of this Part, the owner or operator of the proposed new or modified facility must demonstrate that allowable emission increases from the proposed new or modified facility would not, at a minimum, cause or contribute to air pollution in violation of any national ambient air quality standard in any nonattainment area in accordance with the significance levels in section 231-12.6 of this Subpart.
(f) For the purposes of the required net air quality benefit analysis of Subparts 231-5 and 231-6 of this Part, the owner or operator of the proposed new or modified facility must use the allowable emission increases from the proposed new or modified facility. For the impact offsetting sources, this analysis must use representative actual short term and annual emissions corresponding to the averaging times of the standards. The modeling methods for conducting the net air quality benefit analyses must be approved by the department.