Table 9.3 U.S. National Ambient Air Quality Standards Pollutant Averaging Time Concentration Carbon monoxide(Co Primary 1 hour 35 ppm(40 mg/m) Primary 8 houra 9 ppm(10 mg/m Nitrogen dioxide(NO2), Annual 0.053ppm(100g/m3) Primary and arith. mean Sccondary a Not to be exceeded more than once a year. Sulfur oxides Primary Annual arith. mean 0.03ppm(80μg/m3) Primar 24-houra 0.14 ppm(365 ug/m econdarv 3-houra 0.5ppm(1300g/m3) Particulates(PM10 Primary and Annual arith. mean 50g Secondary Primary 24-houra 150g/m Particulates(PM2.5 Primary and Annual arith.mean° 15μgm3 Secondary Primary 24-hourd Ozone(O3), Primary and I-houre 0.12ppm(245μg/m3) Secondary 8-hour 0.08ppm(163gm3) Lead. Primary and Calendar quarter 1.5pg/m3 SecondaryTable 9.3 U.S. National Ambient Air Quality Standards a Not to be exceeded more than once a year