06-096-100 Me. Code R. § 22
"Building, structure, facility or installation" means all of the pollutant-emitting activities which belong to the same industrial grouping, are located on one or more contiguous or adjacent properties, and are under the control of the same person (or persons under common control). Pollutant-emitting activities shall be considered as part of the same industrial grouping if they belong to the same "Major Group" (i. e. , which have the same two (2)-digit code) as described in the Standard Industrial Classification Manual, 1972, as amended by the 1977 Supplement (United States Government Printing Office stock numbers 4101-0066 and 003-005-00176-0, respectively) or if they have the same six (6)-digit North American industry classification system (NAICS) code available from the U. S. Census Bureau. The requirement for all pollutant emitting activities to belong to the same industrial grouping does not apply to sources subject to Section 112 of the CAA.
06-096 C.M.R. ch. 100, § 22