Virginia Administrative Code

Database updated through January 6, 2011

CHAPTER 30 

AMBIENT AIR QUALITY STANDARDS 

9VAC5-30-10. General. 

A. The provisions of this chapter, unless specified otherwise, shall apply throughout the 

Commonwealth of Virginia. 

B. Ambient air quality standards are required to assure that ambient concentrations of air pollutants 

are consistent with established criteria and shall serve as the basis for effective and reasonable 

management of the air resources of the Commonwealth of Virginia. 

C. Primary ambient air quality standards define levels of air quality which, allowing an adequate 

margin of safety, are necessary to protect the public health. Secondary ambient air quality standards 

define more stringent levels of air quality which are necessary to protect the public welfare from any 

known or anticipated adverse effects associated with the presence of air pollutants in the ambient air. At 

such time as additional pertinent information becomes available with respect to applicable air quality 

criteria, such information will be considered and the ambient air quality standards will be revised 

accordingly. 

D. The absence of a specific ambient air quality standard shall not preclude action by the board to 

control pollutants to assure protection, safety, welfare and comfort of the people of the Commonwealth of 

Virginia. 

E. Where applicable, all measurements of air quality shall be corrected to a reference temperature of 

77 degrees Fahrenheit and to a reference pressure of 14.7 pounds per square inch absolute. 

Statutory Authority 

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 

58. 
Historical Notes 

Derived from VR120-03-01, eff. January 1, 1985; amended, Virginia Register Volume 20, Issue 24, eff. 

September 8, 2004. 

9VAC5-30-15. Reference conditions.

All measurements of air quality that are expressed as mass per unit volume (e.g., micrograms per 

cubic meter) other than for the particulate matter (PM2.5) standards contained in 9VAC5-30-65 and 

9VAC5-30-66 and lead standards contained in 9VAC5-30-80 shall be corrected to a reference 

temperature of 25°C and a reference pressure of 760 millimeters of mercury (1,013.2 millibars). 

Measurements of PM2.5 for purposes of comparison to the standards contained in 9VAC5-30-65 and 

9VAC5-30-66 and of lead for purposes of comparison to the standards contained in 9VAC5-30-80 shall 

be reported based on actual ambient air volume measured at the actual ambient temperature and 

pressure at the monitoring site during the measurement period.

Statutory Authority

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 

58.

Historical Notes

Derived from Virginia Register Volume 23, Issue 21, eff. August 1, 2007; amended, Virginia Register 

Volume 25, Issue 19, eff. June 24, 2009.

9VAC5-30-20. [Repealed] 

Historical Notes 

Derived from VR120-03-02, eff. January 1, 1985; repealed, Virginia Register Volume 15, Issue 12, eff. 

April 1, 1999. 

9VAC5-30-30. Sulfur oxides (sulfur dioxide). 

A. The primary ambient air quality standards are as follows: 

1. 80 micrograms per cubic meter (0.030 parts per million) -- annual arithmetic mean not to be 
exceeded in a calendar year. The annual arithmetic mean shall be rounded to three decimal places 

(fractional parts equal to or greater than 0.0005 ppm shall be rounded up). 

2. 365 micrograms per cubic meter (0.14 parts per million) -- maximum 24-hour concentration not 

to be exceeded more than once per calendar year. The 24-hour averages shall be determined from 

successive nonoverlapping 24-hour blocks starting at midnight each calendar day and shall be 

rounded to two decimal places (fractional parts equal to or greater than 0.005 ppm shall be 

rounded up). 

B. The secondary ambient air quality standard is 1,300 micrograms per cubic meter (0.50 parts per 

million) -- maximum three-hour concentration not to be exceeded more than once per calendar year. The 

3-hour averages shall be determined from successive nonoverlapping 3-hour blocks starting at midnight 

each calendar day and shall be rounded to one decimal place (fractional parts equal to or greater than 

0.05 ppm shall be rounded up). 

C. Sulfur dioxide shall be measured by the reference method described in Appendix A of 40 CFR Part 

50, or other method designated as such, or by an equivalent method. 

D. To demonstrate attainment of the primary standard, the annual arithmetic mean and the secondhighest 24-hour averages must be based upon hourly data that are at least 75% complete in each 

calendar quarter. A 24-hour block average shall be considered valid if at least 75% of the hourly averages 

for the 24-hour period are available. In the event that only 18, 19, 20, 21, 22, or 23 hourly averages are 

available, the 24-hour block average shall be computed as the sum of the available hourly averages using 

18, 19, and so on as the divisor. If fewer than 18 hourly averages are available, but the 24-hour average 

would exceed the level of the standard when zeros are substituted for the missing values, subject to the 

rounding rule of subdivision A 2 of this section, then this shall be considered a valid 24-hour average. In 

this case, the 24-hour block average shall be computed as the sum of the available hourly averages 

divided by 24. 

E. To demonstrate attainment of the secondary standard, the second-highest 3-hour average must be 

based upon hourly data that are at least 75% complete in each calendar quarter. A 3-hour block average 
shall be considered valid only if all three hourly averages for the 3-hour period are available. If only one or 

two hourly averages are available, but the 3-hour average would exceed the level of the standard when 

zeros are substituted for the missing values, subject to the rounding rule of subsection B of this section, 

then this shall be considered a valid 3-hour average. In all cases, the 3-hour block average shall be 

computed as the sum of the hourly averages divided by three. 

Statutory Authority 

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 

58. 

Historical Notes 

Derived from VR120-03-03, eff. January 1, 1985; amended, Virginia Register Volume 20, Issue 24, eff. 

September 8, 2004. 

9VAC5-30-40. Carbon monoxide. 

A. The primary ambient air quality standards are as follows: 

1. Nine parts per million (10 milligrams per cubic meter) -- average eight-hour concentration not to 

be exceeded more than once per year. 

2. 35 parts per million (40 milligrams per cubic meter) -- average one-hour concentration not to be 

exceeded more than once per year. 

B. Carbon monoxide shall be measured by the reference method described in Appendix C of 40 CFR 

Part 50, or other method designated as such, or by an equivalent method. 

C. An 8-hour average shall be considered valid if at least 75% of the hourly averages for the 8-hour 

period are available. In the event that only six (or seven) hourly averages are available, the 8-hour 

average shall be computed on the basis of the hours available using six (or seven) as the divisor. 

D. When summarizing data for comparison with the standards, averages shall be stated to one 

decimal place. Comparison of the data with the levels of the standards in parts per million shall be made 

in terms of integers with fractional parts of 0.5 or greater rounding up. 
Statutory Authority 

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 

58. 

Historical Notes 

Derived from VR120-03-04, eff. January 1, 1985; amended, Virginia Register Volume 20, Issue 24, eff. 

September 8, 2004. 

9VAC5-30-50. Ozone (1-hour). 

A. The primary and secondary ambient air quality standard is 0.12 parts per million (235 micrograms 

per cubic meter). 

B. Ozone shall be measured by the reference method described in Appendix D of 40 CFR Part 50, 

other method designated as such, or by an equivalent method. 

C. The standard is attained when the expected number of days per calendar year with maximum 

hourly average concentrations above 0.12 parts per million (235 micrograms per cubic meter) is equal to 

or less than one, as determined by Appendix H of 40 CFR Part 50. 

D. The 1-hour ozone ambient air quality standard set forth in subsection A of this section shall no 

longer apply to an area after June 15, 2005. 

Statutory Authority 

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 

58. 

Historical Notes 

Derived from VR120-03-05, eff. January 1, 1985; amended, Virginia Register Volume 20, Issue 24, eff.

September 8, 2004. 

9VAC5-30-55. Ozone (8-hour, 0.08 ppm). 

A. The primary and secondary ambient air quality standard is 0.08 parts per million, daily maximum 8-
hour average. 

B. Ozone shall be measured by the reference method described in Appendix D of 40 CFR Part 50, or 

other method designated as such, or by an equivalent method. 

C. The 8-hour primary and secondary ozone ambient air quality standards are met at an ambient air 

quality monitoring site when the average of the annual fourth-highest daily maximum 8-hour average 

ozone concentration is less than or equal to 0.08 ppm, as determined in accordance with Appendix I of 40 

CFR Part 50. 

Statutory Authority 

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 

58.

Historical Notes 

Derived from Virginia Register Volume 20, Issue 24, eff. September 8, 2004; amended, Virginia Register 

Volume 25, Issue 12, eff. March 18, 2009. 

9VAC5-30-56. Ozone (8-hour, 0.075 ppm).

A. The primary and secondary ambient air quality standard is 0.075 parts per million, daily maximum 

8-hour average.

B. Ozone shall be measured by the reference method described in Appendix D of 40 CFR Part 50, 

other method designated as such, or by an equivalent method.

C. The 8-hour primary and secondary ozone ambient air quality standards are met at an ambient air 

quality monitoring site when the three-year average of the annual fourth-highest daily maximum 8-hour 

average ozone concentration is less than or equal to 0.075 ppm, as determined in accordance with 

Appendix P to 40 CFR Part 50. 

Statutory Authority

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 

58.
Historical Notes

Derived from Virginia Register Volume 25, Issue 12, eff. March 18, 2009.

9VAC5-30-60. Particulate matter (PM10). 

A. 1. The primary and secondary 24-hour ambient air quality standard is 150 micrograms per cubic 

meter--24-hour average concentration.

2. The standard is attained when the expected number of days per calendar year with a 24-hour 

average concentration above 150 micrograms per cubic meter, as determined in accordance with 

Appendix K of 40 CFR Part 50, is equal to or less than one.

B. (Reserved.)

C. For the purpose of determining attainment of the primary and secondary standards, particulate 

matter shall be measured in the ambient air as PM10 (particles with an aerodynamic diameter less than or 

equal to a nominal 10 micrometers) by a reference method based on Appendix J of 40 CFR Part 50, or 

other method designated as such, or by an equivalent method.

Statutory Authority 

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 

58. 

Historical Notes 

Derived from VR120-03-06, eff. July 1, 1988; amended, Virginia Register Volume 20, Issue 24, eff. 

September 8, 2004; Volume 23, Issue 21, eff. August 1, 2007. 

9VAC5-30-65. Particulate matter (PM2.5). 

A. The primary and secondary ambient air quality standards for particulate matter are:

1. 15.0 micrograms per cubic meter -- annual arithmetic mean concentration.

2. 65 micrograms per cubic meter -- 24-hour average concentration.

B. Particulate matter shall be measured in the ambient air as PM2.5 (particles with an aerodynamic 
diameter less than or equal to a nominal 2.5 micrometers) by a reference method based on Appendix L of 

40 CFR Part 50, or other method designated as such, or by an equivalent method.

C. The annual primary and secondary PM2.5 standards are met when the annual arithmetic mean 

concentration, as determined in accordance with Appendix N of 40 CFR Part 50, is less than or equal to 

15.0 micrograms per cubic meter.

D. The 24-hour primary and secondary PM2.5 standards are met when the 98th percentile 24-hour 

concentration, as determined in accordance with Appendix N of 40 CFR Part 50, is less than or equal to 

65 micrograms per cubic meter.

E. The PM2.5 standards set forth in this section were established by EPA on July 18, 1997 (62 FR 

38652) and became effective on September 8, 2004, by adoption by the board. The PM2.5 standards set 

forth in this section shall continue to apply only for purposes of the following:

1. Control strategy implementation plan revisions, maintenance plans, and associated emissions 

budgets relative to the PM2.5 standards in this section.

2. Designation of nonattainment areas and maintenance areas relative to the PM2.5 standards in 

this section.

Nothing in this section shall prevent the redesignation of any nonattainment area to attainment at any 

time.

Statutory Authority 

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 

58. 

Historical Notes 

Derived from Virginia Register Volume 20, Issue 24, eff. September 8, 2004; amended, Virginia Register 

Volume 23, Issue 21, eff. August 1, 2007; Volume 25, Issue 12, eff. March 18, 2009. 

9VAC5-30-66. Particulate matter (PM2.5).

A. The primary and secondary ambient air quality standards for particulate matter are:
1. 15.0 micrograms per cubic meter annual arithmetic mean concentration.

2. 35 micrograms per cubic meter, 24-hour average concentration measured in the ambient air as 

PM2.5 (particles with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers).

B. Particulate matter shall be measured in the ambient air as PM2.5 (particles with an aerodynamic 

diameter less than or equal to a nominal 2.5 micrometers) by a reference method based on Appendix L of 

40 CFR Part 50, or other method designated as such, or an equivalent method.

C. The annual primary and secondary PM2.5 standards are met when the annual arithmetic mean 

concentration, as determined in accordance with Appendix N of 40 CFR Part 50, is less than or equal to 

15.0 micrograms per cubic meter.

D. The 24-hour primary and secondary PM2.5 standards are met when the 98th percentile 24-hour 

concentration, as determined in accordance with Appendix N of 40 CFR Part 50, is less than or equal to 

35 micrograms per cubic meter.

E. The PM2.5 standards set forth in this section were established by EPA on October 17, 2006 (71 FR 

61224), and shall become effective in the Commonwealth on August 1, 2007. The PM2.5 standards set 

forth in this section shall apply for purposes of the following:

1. Control strategy implementation plan revisions, maintenance plans, and associated emissions 

budgets relative to the PM2.5 standards in this section.

2. Designation of nonattainment areas and maintenance areas relative to the PM2.5 standards in 

this section.

3. Implementation of the new source review programs set forth in Part II (9VAC5-80-50 et seq.) of 

9VAC5-80 (Permits for Stationary Sources).

Nothing in this section shall prevent the redesignation of any nonattainment area to attainment at any 

time.

Statutory Authority

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 
58.

Historical Notes

Derived from Virginia Register Volume 23, Issue 21, eff. August 1, 2007.

9VAC5-30-70. Oxides of nitrogen with nitrogen dioxide as the indicator. 

A. The primary annual ambient air quality standard is 53 parts per billion (ppb), annual average 

concentration, measured in the ambient air as nitrogen dioxide. 

B. The primary 1-hour ambient air quality standard is 100 ppb, 1-hour average concentration, annual 

arithmetic mean concentration.

C. The secondary ambient air quality standard is 0.053 parts per million (ppm) (100 micrograms per 

cubic meter), annual arithmetic mean concentration.

D. The levels of the standards shall be measured by a reference method based on Appendix F of 40 

CFR Part 50, or by a federal equivalent method (FEM) designated in accordance with 40 CFR Part 53. 

E. The annual primary standard is met when the annual average concentration in a calendar year is 

less than or equal to 53 ppb, as determined in accordance with Appendix S of 40 CFR Part 50 for the 

annual standard. 

F. The 1-hour primary standard is met when the three-year average of the annual 98th percentile of 

the daily maximum 1-hour average concentration is less than or equal to 100 ppb, as determined in 

accordance with Appendix S of 40 CFR Part 50 for the 1-hour standard.

G. The secondary standard is attained when the annual arithmetic mean concentration in a calendar 

year is less than or equal to 0.053 ppm, rounded to three decimal places (fractional parts equal to or 

greater than 0.0005 ppm must be rounded up). To demonstrate attainment, an annual mean shall be 

based upon hourly data that are at least 75% complete or upon data derived from manual methods that 

are at least 75% complete for the scheduled sampling days in each calendar quarter.

Statutory Authority 

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 
58. 

Historical Notes 

Derived from VR120-03-07, eff. January 1, 1985; amended, Virginia Register Volume 20, Issue 24, eff. 

September 8, 2004; Volume 26, Issue 23, eff. August 18, 2010. 

9VAC5-30-80. Lead.

A. The primary and secondary ambient air quality standard for lead and its compounds is 1.5 

micrograms per cubic meter, maximum arithmetic mean averaged over a calendar quarter, measured as 

elemental lead by a reference method based on Appendix G of 40 CFR Part 50, or by an equivalent 

method. 

B. The standards set forth in subsection A of this section shall remain applicable to all areas 

notwithstanding the ambient air quality standard in subsection C of this section. The lead standard set 

forth in subsection A of this section shall no longer apply to an area one year after the effective date of the 

designation of that area, pursuant to § 107 of the federal Clean Air Act, for the lead ambient air quality 

standard set forth in subsection C of this section.

C. The primary and secondary ambient air quality standard for lead and its compounds is 0.15 

micrograms per cubic meter, maximum arithmetic mean averaged over a three-month period, measured 

as lead either by (i) a reference method based on Appendix G of 40 CFR Part 50 and designated in 

accordance with 40 CFR Part 53; or (ii) an equivalent method designated in accordance with 40 CFR Part 

53. The primary and secondary ambient air quality standards for lead are met when the maximum 

arithmetic three-month mean concentration for a three-year period, as determined in accordance with 

Appendix R of 40 CFR Part 50, is less than or equal to 0.15 micrograms per cubic meter.

Statutory Authority 

§ 10.1-1308 of the Code of Virginia; §§ 108, 109 and 302 of the Clean Air Act; 40 CFR Parts 50, 53 and 

58. 

Historical Notes 
Derived from VR120-03-08, eff. January 1, 1985; amended, Virginia Register Volume 20, Issue 24, eff. 

September 8, 2004; Volume 25, Issue 19, eff. June 24, 2009.