How is the 8-hour ozone concentration-based
standard calculated? First, identify the concentration at the
4th highest 8-h daily maximum. Second, average the 4th highest
value for each of the last 3 years. The 8-hour standard is based
on the concept that if the 3-year average of the 4th highest
8-hour daily maximum is greater than or equal to 0.085 ppm, the
area will be in violation of the current standard. For the revised
8-hour ozone standard, attainment occurs when the 3-year average
of the 4th highest 8-hour daily maximum concentration is equal
to or less than 0.075 ppm.
Calculating the 8-Hour Ozone Standard