35 Ill. Adm. Code 204.1000
Stack Heights
Section 204.1000 Stack Heights
a) The
degree of emission limitation required for control of any air pollutant under
this Part shall not be affected in any manner by:
1) So
much portion of the stack height of any source that exceeds good engineering
practice; or
2) Any
other dispersion technique.
b) Subsection
(a) shall not apply with respect to stack heights in existence before December
31, 1970 or to dispersion techniques implemented before then.