How is the 8-hour ozone concentration-based
standard calculated? Unlike the form of the previous 0.075 ppm
8-hour average ozone standard that was established in 2008, the
daily maximum 8-hour average concentration for a given day is
derived from the highest of the 17 consecutive 8-hour averages
beginning with the 8-hour period from 7:00 a.m. to 3:00 p.m.
and ending with the 8-hour period from 11:00 p.m. to 7:00 a.m.
the following day (i.e., the 8-hour averages for start time 7:00
a.m. to start time 11:00 p.m.). The 17 consecutive 8-hour averages
are as follows:
7:00 a.m. to 3:00 p.m.
8:00 a.m. to 4:00 p.m.
9:00 a.m. to 5:00 p.m.
10:00 a.m. to 6:00 p.m.
11:00 a.m. to 7:00 p.m.
12:00 p.m. to 8:00 p.m.
1:00 p.m. to 9:00 p.m.
2:00 p.m. to 10:00 p.m.
3:00 p.m. to 11:00 p.m.
4:00 p.m. to 12:00 a.m.
5:00 p.m. to 1:00 a.m.
6:00 p.m. to 2:00 a.m.
7:00 p.m. to 3:00 a.m.
8:00 p.m. to 4:00 a.m.
9:00 p.m. to 5:00 a.m.
10:00 p.m. to 6:00 a.m.
11:00 p.m. to 7:00 a.m.
Once this calculation is made, identify
the concentration at the 4th highest 8-h daily maximum during
the year. 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 0.071 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 0.070
ppm.
For more information, please see page 65459
at: https://www.govinfo.gov/content/pkg/FR-2015-10-26/pdf/2015-26594.pdf
Calculating the 8-Hour Ozone Standard