Return air systems.
Municipal Code of Chicago § 18-28-606.2.1
in effect18-28-606.2.1 Return air systems.
Smoke detectors shall be installed in return air systems with a design capacity greater than 2,000 cfm (0.9 m 3 /s), in the return air duct or plenum upstream of any filters, exhaust air connections, outdoor air connections, or decontamination equipment and appliances.
Exception: Smoke detectors are not required in the return air system where the space served by the air distribution system is protected by a system of area smoke detectors in accordance with Section 907 of the Chicago Building Code. The area smoke detector system shall comply with Section 18-28-606.4.
(Amend Coun. J. 11-9-16, p. 36266, § 36; Amend Coun. J. 4-10-19, p. 100029, Art. XII, § 8; Amend Coun. J. 9-14-21, p. 35949, Art. VI, § 8)
Source: City of Chicago, Municipal Code of Chicago (American Legal Publishing, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/chicago/latest/chicago_il/0-0-0-2687650Fetched: 10/24/2026