Pollutant

Averaging Time

Air Quality Area Designation

Class I

Class II

Class III

SO₂ (µg/m³)^*

Annual

0.10

1.0

1.0

24-hour

0.20

5.0

5.0

3-hour

1.0

25.0

25.0

PM₁₀ (µg/m³)

Annual

0.20

0.2

0.2

24-hour

0.30

1.0

1.0

PM_2.5 (µg/m³)

Annual

0.06

0.3

0.3

24-hour

0.07

1.2

1.2

NO₂ (µg/m³)

Annual

0.10

1.0

1.0

CO (mg/m³)^**

8 hour

---

0.5

0.5

1-hour

---

2.0

2.0

^* micrograms/cubic meter

^**milligrams/cubic meter