(a) During any 12 consecutive months, 99 percent1 of the three-hour average concentrations shall not exceed 0.25 ppm and the three-hour average concentration shall not exceed 0.50 ppm2 more than once a year. (Applicable in all levels).
(b) During any 12 consecutive months, 99 percent3 of the 24-hour average concentrations shall not exceed 0.10 ppm; and the 24-hour average concentration shall not exceed 0.14 ppm4 more than once a year. (Applicable in all levels).
(c) During any 12 consecutive months, the annual average of the 24-hour average concentrations shall not exceed 0.03 ppm5. (Applicable in all levels.)