National Ambient Air Quality Standards (NAAQS)
|8-hour average||9 ppm||9 ppm||(1)|
|1-hour average||35 ppm||35 ppm||(1)|
|3-month rolling average||0.15 µg/m3||0.15 µg/m3||(2)|
|Quarterly average||1.5 µg/m3||1.5 µg/m3|
|1-hour average||0.100 ppm||—||(3)|
|Annual average||0.053 ppm||0.053 ppm|
|8-hour average||0.070 ppm||0.070 ppm||(4)|
|PM10 (Inhalable Particulates)|
|Annual average||50 µg/m3||50 µg/m3||(5)|
|24-hour average||150 µg/m3||150 µg/m3||(6)|
|PM2.5 (Fine Particulates)|
|Annual average||12 µg/m3||15 µg/m3|
|24 hour average||35 µg/m3||35 µg/m3||(7)|
|1-hour average||0.75 ppm||—||(8)|
|3-hour average||—||0.50 ppm||(1)|
(1) This average is not to be exceeded more than once per year.
(2) The lead standard was revised 10/15/2008.
(3) The standard is attained when the 3-year average of the 98th percentile of the annual distribution of daily maximum 1-hour average concentrations is less than the standard. The NO2 standard was revised 1/22/2010.
(4) The standard is attained when the three-year average of the fourth-highest daily maximum 8-hour average is less than or equal to the standard. The ozone standard was revised 10/26/2015.
(5) The standard is attained when the expected annual arithmetic mean concentration, as determined in accordance with Appendix K to 40 CFR 50, is less than or equal to the standard.
(6) The standard is attained when the 3-year average of the annual 99th percentile concentration is less than the standard.
(7) The standard is attained when the 98th percentile concentration for the year is less than the standard. The PM2.5standard was revised 1/15/2013.
(8) 99th percentile, averaged over 3 years.