| Pollutant | Averaging Time | Level 1 | Level 2 |
|---|---|---|---|
| Sulfur Dioxide (SO2) | 24 hr. | 0.6 ppm (1600 µg/M³) | 0.8 ppm (2100 µg/M³) |
| Inhalable Particulate Matter (PM10)* | 24 hr. | 420 µg/M³ | 500 µg/M³ |
| Carbon Monoxide | 8 hr. | 30 ppm (34 mg/M³) | 40 ppm (46 mg/M³) |
| Ozone | 1 hr. | 0.4 ppm (800 µg/M³) | 0.5 ppm (1000 µg/M³) |
| Nitrogen Dioxide | 1 hr. | 1.2 ppm (2260 µg/M³) | 1.6 ppm (3000 µg/M³) |
| 24 hr. | 0.3 ppm (565 µg/M³) | 0.4 ppm (750 µg/M³) | |
ppm = parts per million by volume
µg = microgram
mg = milligram
M³ = cubic meter
* THESE CRITERIA DO NOT APPLY TO EPISODES CAUSED BY DUST STORMS.