R18-2-218. Limitation of Pollutants in Classified Attainment Areas

A. Areas designated as Class I, II, or III shall be limited to the following increases in air pollutant 

concentrations occurring over the baseline concentration; provided that for any period other 

than an annual period, the applicable maximum allowable increase may be exceeded once per 

year at any one location:

CLASS I

Maximum Allowable

Increase (Micrograms

per cubic meter)

Particulate matter: PM2.5

Annual arithmetic mean 1

24-hr maximum 2

Particulate matter: PM10

Annual arithmetic mean 4

24-hour maximum 8

Sulfur dioxide:

Annual arithmetic mean 2

24-hour maximum 5

3-hour maximum 25

Nitrogen dioxide:

Annual arithmetic mean 2.5

CLASS II

Particulate matter: PM2.5

Annual arithmetic mean 4

24-hr maximum 9

Particulate matter: PM10

Annual arithmetic mean 17

24-hour maximum 30

Sulfur dioxide:

Annual arithmetic mean 20

24-hour maximum 91

3-hour maximum 512

Nitrogen dioxide:

Annual arithmetic mean 25

CLASS III
Particulate matter: PM2.5

Annual arithmetic mean 8

24-hr maximum 18

Particulate matter: PM10

Annual arithmetic mean 34

24-hour maximum 60

Sulfur dioxide:

Annual arithmetic mean 40

24-hour maximum 182

3-hour maximum 700

Nitrogen dioxide:

Annual arithmetic mean 50

B. The baseline concentration shall be that ambient concentration level which exists in the baseline 

area at the time of the applicable minor source baseline data.

1. The major source baseline date is:

a. January 6, 1975, for sulfur dioxide and PM10.

b. February 8, 1988, for nitrogen dioxide.

c. October 20, 2010, for PM2.5.

2. The minor source baseline date shall be the earliest date after the trigger date on which a 

major source as defined in R18-2-401 or major modification subject to 40 CFR 52.21 or 

R18-2-406 submits a complete application under the relevant regulations. The trigger date 

is:

a. August 7, 1977, for PM10 and sulfur dioxide.

b. February 8, 1988, for nitrogen dioxide.

c. October 20, 2011, for PM2.5.

3. A baseline concentration shall be determined for each pollutant for which there is a minor 

source baseline date and shall include both:

a. The actual emissions representative of sources in existence on the minor source baseline 

date, except as provided in subsection (B)(4); and

b. The allowable emissions of major sources as defined in R18-2-401 which commenced 

construction before the major source baseline date but were not in operation by the 

applicable minor source baseline date.

4. The following shall not be included in the baseline concentration and shall affect the 

applicable maximum allowable increase:

a. Actual emissions from any major source as defined in R18-2-401 on which construction 

commenced after the major source baseline date; and

b. Actual emissions increases and decreases at any stationary source occurring after the 

minor source baseline date.

C. The baseline date shall be established for each pollutant for which maximum allowable 

increases or other equivalent measures have been established if both:
1. The area in which the proposed source or modification would construct is designated as 

attainment or unclassifiable under section 107(d)(1)(A)(ii) or (iii) of the Act for the 

pollutant on the date of its complete application under 40 CFR 52.21 or R18-2-406; and

2. In the case of a major source as defined in R18-2-401, the pollutant would be emitted in 

significant amounts, or in the case of a major modification, there would be a significant net 

emissions increase of the pollutant.

D. The baseline area shall be the AQCR that contains the area, designated as attainment or 

unclassifiable under section 107(d)(1)(A)(ii) or (iii) of the Act, in which the major source as 

defined in R18-2-401 or major modification establishing the minor source baseline date would 

construct or would have an air quality impact for the pollutant for which the minor source 

baseline date is established, as follows: greater than or equal to 1 microgram per cubic meter 

(annual average) for sulfur dioxide, nitrogen dioxide or PM10; or greater than or equal to 0.3 

microgram per cubic meter (annual average) for PM2.5. Area redesignations under R18-2-217 

that would redesignate a baseline area may not intersect or be smaller than the area of impact 

of any new major source as defined in R18-2-401 or a major modification which either:

1. Establishes a minor source baseline date, or

2. Is subject to either 40 CFR 52.21 or R18-2-406 and would be constructed in Arizona.

E. The maximum allowable concentration of any air pollutant in any area to which subsection (A) 

applies shall not exceed a concentration for each pollutant equal to the concentration permitted 

under the ambient air quality standards contained in this Article.

F. For purposes of determining compliance with the maximum allowable increases in ambient 

concentrations of an air pollutant, the following concentrations of such pollutant shall not be 

taken into account:

1. Concentration of such pollutant attributable to the increase in emissions from major and 

stationary sources which have converted from the use of petroleum products, or natural 

gas, or both, by reason of a natural gas curtailment order which is in effect under the 

provisions of sections 2(a) and (b) of the Energy Supply and Environmental Coordination 

Act of 1974, 15 U.S.C. 792, over the emissions from such sources before the effective date 

of such order;

2. The concentration of such pollutant attributable to the increase in emissions from major and 

stationary sources which have converted from using gas by reason of a natural gas 

curtailment plan in effect pursuant to the Federal Power Act, 16 U.S.C. 792 - 825r, over 

the emissions from such sources before the effective date of the natural gas curtailment 

plan;

3. Concentrations of PM10 attributable to the increase in emissions from construction or other 

temporary activities of a new or modified source;

4. The increase in concentrations attributable to new sources outside the United States over the 

concentrations attributable to existing sources which are included in the baseline 

concentration; and

5. Concentrations attributable to the temporary increase in emissions of sulfur dioxide, nitrogen 

oxides, or PM10 from major sources as defined in R18-2-401 when the following conditions 

are met:

a. The operating permit issued to such sources specifies the time period during which the 

temporary emissions increase of sulfur dioxide, nitrogen oxides, or PM10 would occur. 

Such time period shall not be renewable and shall not exceed two years unless a longer 

period is specifically approved by the Director.
b. No emissions increase shall be approved which would either:

i. Impact any portion of any Class I area or any portion of any other area where an 

applicable incremental ambient standard is known to be violated in that portion; or

ii. Cause or contribute to the violation of a state ambient air quality standard.

c. The operating permit issued to such sources specifies that, at the end of the time period 

described in subsection (F)(5)(a), the emissions levels from the sources would not 

exceed the levels occurring before the temporary emissions increase was approved.

6. The exception granted with respect to increment consumption under subsections (F)(1) and 

(2) shall not apply more than five years after the effective date of the order or natural gas 

curtailment plan on which the exception is based.

G. If the Director or the Administrator determines that the SIP is substantially inadequate to 

prevent significant deterioration or that an applicable maximum allowable increase as specified 

in subsection (A) is being violated, the SIP shall be revised to correct the inadequacy or the 

violation. The SIP shall be revised within 60 days of such a finding by the Director or within 

60 days following notification by the Administrator, or by such later date as prescribed by the 

Administrator after consultation with the Director.

H. The Director shall review the adequacy of the SIP on a periodic basis and within 60 days of 

such time as information becomes available that an applicable maximum allowable increase is 

being violated.

Historical Note

Adopted effective May 14, 1979 (Supp. 79-1). Amended effective October 2, 1979 (Supp. 

79-5). Editorial correction, subsection (A), paragraph (5), subparagraph (d) (Supp. 80-2). 

Amended effective May 28, 1982 (Supp. 82-3). Former Section R9-3-217 renumbered 

without change as Section R18-2-217 (Supp. 87-3). Former Section R18-2-218 

renumbered to R18-2-219, new Section R18-2-218 renumbered from R18-2- 217(B) and 

amended effective September 26, 1990 (Supp. 90-3). Amended effective November 15, 

1993 (Supp. 93-4). Amended effective February 28, 1995 (Supp. 95-1). Amended by 

final rulemaking at 18 A.A.R. 1542, effective August 7, 2012 (Supp. 12-2).

R18-2-219. Repealed

Historical Note

Adopted effective May 14, 1979 (Supp. 79-1). Former Section R9-3-218 repealed, new 

Section R9-3-218 adopted effective September 22, 1983 (Supp. 83-5). Former Section 

R9-3-218 renumbered without change as Section R18-2-218 (Supp. 87-3). Former 

Section R18-2-219 renumbered to R18-2-220, new Section R18-2-219 renumbered from 

R18-2-218 and amended effective September 26, 1990 (Supp. 90-3). Section repealed by 

final rulemaking at 18 A.A.R. 1542, effective August 7, 2012 (Supp. 12-2).