92 Ill. Adm. Code 442.205
Aisle
Section 442
Section 442.205 Aisle
a) Minimum clearance of all aisles, including the aisle (or
passageway) leading to an emergency door in the rear, shall be 12 inches.
b) A dedicated aisle which conforms to 49 CFR 571.217 may be
adjacent to any side emergency door.