Where lower-combustion air openings connect with crawl spaces, such spaces shall have unobstructed openings to the outdoors at least twice that required for the combustion air openings. The height of the crawl space shall comply with the requirements of the Chicago Building Code and shall be without obstruction to the free flow of air.
In addition, the lowest side of combustion air openings connecting with crawl spaces shall be a minimum of 12 inches (300 mm) above the adjoining grade level.
(Amend Coun. J. 9-14-21, p. 35949, Art. VII, § 1)