Important: This information is published as soon as the values are detected, and does not imply that the data have passed quality assurance validation procedures.
The EPA air quality standard for ozone, designed to protect public health with an adequate margin of safety, is 0.085 parts per million (ppm), averaged over 8 hours. For concentrations greater than 0.085 ppm, the air is considered to be unhealthful.
Each data point represents an average of the ozone concentrations for the previous eight hours. For example, the data point graphed at hour 22 (10 p.m.) represents the average of the ozone levels from hour 14 to hour 22 (2 p.m. to 10 p.m.), not the actual ozone level at hour 22. The next data point, graphed at hour 23 (11 p.m.), represents the average of the ozone levels from hour 15 to hour 23 (3 p.m. to 11 p.m.), and so on.
Note: If more than 2 hours are missing from an 8 hour data set, the average is not calculated.
In March 2008, EPA strengthened the air quality standards for ground-level ozone, a primary component of smog. These new standards mean that lower levels of ozone will now be reported as unhealthy in the daily smog forecasts and in the Air Quality Index (AQI). This website reflects this change.
| Related Info |
| Today's Readings (ppmv, 8 hour average) at the South Dekalb Station |
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| Note: Each data point represents the EPA standard average ozone readings over the previous eight-hour period (click here for more information). Hourly ozone readings (raw data) are also available. | ||||||
| Period Ending: |
8-hour Average: |
Period Ending: |
8-hour Average: |
Period Ending: |
8-hour Average: |
 |
| 01 | .011 | 09 | .000 | 17 | N/A | |
| 02 | .006 | 10 | .000 | 18 | N/A | |
| 03 | .001 | 11 | N/A | 19 | .038 | |
| 04 | .000 | 12 | N/A | 20 | .041 | |
| 05 | .000 | 13 | N/A | 21 | .040 | |
| 06 | .000 | 14 | N/A | 22 | .038 | |
| 07 | .000 | 15 | N/A | 23 | .033 | |
| 08 | .000 | 16 | N/A | 24 | .027 | |