1. a) Ductwork has not been modified so as to interconnect such fuel combustion emission units;
2. b) The actual heat input to any such fuel combustion emission units is not increased; and
3. c) No new fuel combustion emission unit is added to reduce the degree of control of emissions of particulate matter required by this Subpart.

Section 212.207 of this Subpart may be applied to the aggregate of all fuel combustion emission units for which construction or modification commenced prior to April 14, 1972, vented to a common stack provided that after January 26, 1972:

(Source: Amended at 20 Ill. Reg. 7605, effective May 22, 1996)