Stage 1 Smog Alerts
Number of Basin-Days Exceeding Health Standard Levelsa)
ppm = parts per million parts of air, by volume.
* The federal 8-hour ozone standard was revised from 0.08 ppm to 0.075 ppm, effective May 27, 2008.
a) Basin-days represents the number of days a standard was exceeded anywhere in the South Coast Air Basin.
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