020-2 Wyo. Code R. § 2-4 - Ambient standards for sulfur oxides
(a) The level of
the primary 1-hour annual ambient air quality standard for oxides of sulfur is
75 parts per billion (ppb, which is 1 part in 1,000,000,000), measured in the
ambient air as sulfur dioxide (SO2).
(i) The 1-hour primary standard is met at an
ambient air quality monitoring site when the three-year average of the annual
(99th percentile) of the daily maximum 1-hour average concentrations is less
than or equal to 75 ppb, as determined in accordance with Appendix T of 40 CFR
part 50.
(b) The level of the secondary 3-hour ambient
air quality standard for oxides of sulfur is 0.5 parts per million (ppm, which
is 1 part in 1,000,000), not to be exceeded more than once per calendar year.
The 3-hour averages shall be determined from successive nonoverlapping 3-hour
blocks starting at midnight each calendar day and shall be rounded to 1 decimal
place (fractional parts equal to or greater than 0.05 ppm shall be rounded up).
(i) Sulfur oxides shall be measured in the
ambient air as sulfur dioxide by the reference method described in Appendix A
of 40 CFR part 50 or by an equivalent method designated in accordance with 40
CFR part 53.
(ii) To demonstrate
attainment, the second-highest 3-hour average must be based upon hourly data
that are at least 75 percent complete in each calendar quarter. A 3-hour block
average shall be considered valid only if all three hourly averages for the
3-hour period are available. If only one or two hourly averages are available,
but the 3-hour average would exceed the level of the standard when zeros are
substituted for the missing values, subject to the rounding rule of paragraph
(b) of this section, then this shall be considered a valid 3-hour average. In
all cases, the 3-hour block average shall be computed as the sum of the hourly
averages divided by 3.
Notes
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