; or (ii) to restore, maintain, or improve the reliability of operations at, or the safety of, the source, except, with respect to either clause (i) or (ii), when the change would be a modification as defined in subparagraph (A) and the Administrator determines that the increase in the maximum achievable hourly emission rate of a pollutant from such change would cause an adverse effect on human health or the environment. . 3. Clarification of definition of construction for prevention of significant deterioration Subparagraph (C) of section 169(2) of the Clean Air Act ( 42 U.S.C. 7479(2) ) is amended to read as follows: (C) The term construction , when used in connection with a major emitting facility, includes a modification (as defined in section 111(a)) at such facility, except that for purposes of this subparagraph a modification does not include a change at a major emitting facility that does not result in a significant emissions increase, or a significant net emissions increase, in annual actual emissions at such facility. . 4. Clarification of definition of modifications and modified for nonattainment areas Paragraph (4) of section 171 of the Clean Air Act ( 42 U.S.C. 7501 ) is amended to read as follows: (4) The terms modifications and modified mean a modification as defined in section 111(a)(4), except that such terms do not include a change at a major emitting facility that does not result in a significant emissions increase, or a significant net emissions increase, in annual actual emissions at such facility. . 5. Rule of construction Nothing in this Act or the amendments made by this Act shall be construed to treat any change as a modification for purposes of any provision of the Clean Air Act ( 42 U.S.C. 7401 et seq. ) if such change would not have been so treated as of the day before the date of enactment of this Act.