e) Class I Variances. The owner or operator of a proposed source or modification may demonstrate to the Federal Land Manager that the emissions from such source or modification would have no adverse impact on the air quality related values of any such lands (including visibility), notwithstanding that the change in air quality resulting from emissions from such source or modification would cause or contribute to concentrations that would exceed the maximum allowable increases for a Class I area. If the Federal Land Manager concurs with such demonstration and so certifies, the Agency may, provided that the applicable requirements of this Part are otherwise met, issue the permit with such emission limitations as may be necessary to assure that emissions of SO₂, PM_2.5, PM₁₀, and NO_X would not exceed the following maximum allowable increases over minor source baseline concentration for such pollutants:

h) Emissions Limitations for Presidential or Gubernatorial Variance. In the case of a permit issued under subsection (f) or (g), the source or modification shall comply with such emission limitations as may be necessary to assure that emissions of SO₂ from the source or modification would not (during any day on which the otherwise applicable maximum allowable increases are exceeded) cause or contribute to concentrations that would exceed the following maximum allowable increases over the baseline concentration and to assure that such emissions would not cause or contribute to concentrations that exceed the otherwise applicable maximum allowable increases for periods of exposure of 24 hours or less for more than 18 days, not necessarily consecutive, during any annual period: