(1) The following concentrations will be excluded in determining compliance with a maximum allowable increase:
(a) concentrations attributable to the increase in emissions from stationary sources which have converted from the use of petroleum products, natural gas, or both by reason of an order in effect under sections 2(a) and (b) of the Energy Supply and Environmental Coordination Act of 1974, 15 USC 791, et seq. (1988) , over the emissions from such sources before the effective date of such an order;
(b) concentrations attributable to the increase in emissions from sources which have converted from using natural gas by reason of a natural gas curtailment plan in effect pursuant to the Federal Power Act, 16 USC 791a, et seq. (1988 and Supp. III 1991) , over the emissions from such sources before the effective date of such plan;
(c) concentrations of particulate matter attributable to the increase in emissions from construction or other temporary emission-related activities of new or modified sources;
(d) the increase in concentrations attributable to new sources outside the United States over the concentrations attributable to existing sources which are included in the baseline concentration; and
(e) concentrations attributable to the temporary increase in emissions of sulfur dioxide, particulate matter, or nitrogen oxides from stationary sources meeting the criteria specified in (3) .
(2) With respect to (1) (a) or (b) , no exclusion of such concentrations shall apply more than five years after the effective date of the order to which (1) (a) refers, or the plan to which (1) (b) refers, whichever is applicable. If both such order and plan are applicable, no such exclusion shall apply more than five years after the later of such effective dates.
(3) For purposes of excluding concentrations pursuant to (1) (e) :
(a) The time period for a temporary increase in emissions may not exceed two years and is not renewable.
(b) No emissions increase from a stationary source would be allowed which would:
(i) impact a Class I area or an area where an applicable increment is known to be violated; or
(ii) cause or contribute to the violation of a national ambient air quality standard.