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Combustion Air (18-28-701 et seq.)

Municipal Code of Chicago tit. 18, ch. 18-28, art. VII
in effect

Municipal Code of Chicago § 18-28-701.2 Combustion and dilution air required.

18-28-701.2 Combustion and dilution air required. Every room or space containing fuel-burning appliances shall be provided with combustion and dilution air as required by this chapter. Combustion and dilution air shall be provided in accordance with Sections 18-28-702, 18-28-703, 18-28-704, 18-28-706 or 18-28-707 shall be provided by an approved engineered system. Direct vent appliances or equipment that do not draw combustion air from inside of the building are not required to be considered in the determination of the combustion and dilution air requirements. Combustion air requirements shall be determined based on the simultaneous operation of all fuel-burning appliances drawing combustion and dilution air from the room or space. (Amend Coun. J. 11-8-12, p. 38872, § 321; Amend Coun. J. 9-14-21, p. 35949, Art. VII, § 1)

Municipal Code of Chicago § 18-28-701.3 Circulation of air.

18-28-701.3 Circulation of air. The equipment and appliances within every room containing fuel-burning appliances shall be installed so as to allow free circulation of air. Provisions shall be made to allow for the simultaneous operation of mechanical exhaust systems, fireplaces or other equipment and appliances operating in the same room or space from which combustion and dilution air is being drawn. Such provisions shall prevent the operation of such appliances, equipment and systems from affecting the supply of combustion and dilution air.

Municipal Code of Chicago § 18-28-701.4 Crawl space and attic space.

18-28-701.4 Crawl space and attic space. For the purposes of this chapter, an opening to a naturally ventilated crawl space or attic space shall be considered equivalent to an opening to the outdoors.

Municipal Code of Chicago § 18-28-701.4.1 Crawl space.

18-28-701.4.1 Crawl space. 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)

Municipal Code of Chicago § 18-28-701.4.2 Attic space.

18-28-701.4.2 Attic space. Where combustion air is obtained from an attic area, the attic ventilating openings shall not be subject to ice or snow blockage, and the attic shall have not less than 30 inches (762 mm) vertical clear height at its maximum point. Attic ventilation openings shall be sufficient to provide the required volume of combustion air and the attic ventilation required by the Chicago Building Code. The combustion air openings shall be provided with a sleeve of not less than 0.019 inch (0.5 mm) (No. 26 Gauge) galvanized steel or other approved material extending from the appliance enclosure to at least 6 inches (152 mm) above the top of the ceiling joists and insulation. (Amend Coun. J. 9-14-21, p. 35949, Art. VII, § 1)

Municipal Code of Chicago § 18-28-701.5 Prohibited sources.

18-28-701.5 Prohibited sources. Openings and ducts shall not connect appliance enclosures with a space in which the operation of a fan will adversely affect the flow of combustion air. Combustion air shall not be obtained from a hazardous location, except where the fuel-fired appliances are located within the hazardous location and are installed in accordance with the Chicago Building Code. Combustion air shall not be taken from a refrigeration machinery room. (Amend Coun. J. 9-14-21, p. 35949, Art. VII, § 1)

Municipal Code of Chicago § 18-28-701.5.1

18-28-701.5.1 The remaining space surrounding a chimney liner, gas vent, special gas vent, or plastic piping installed within a masonry, metal or factory built chimney, shall not be used to supply combustion air. Exception: Direct vent gas-fired appliances designed for installation in a solid fuel burning fireplace where installed in accordance with the listing and the manufacturer's instruction.

Municipal Code of Chicago § 18-28-702.1 Unconfined spaces.

18-28-702.1 Unconfined spaces. Fuel burning space heating and/or water heating equipment with a combined input rating greater than 150,000 Btu/hour shall be provided with air from outdoors for combustion and dilution using the methods described in Section 18-28-703.3. Exception: Single-family and two-family dwellings (including townhouses) are not required to use outdoor air for combusting and dilution. Such dwellings shall be provided with air for combustion and dilution in accordance with Sections 18-28-702, 18-28-703.2, or 18-28-703.3. Fuel-burnings heating equipment and/or water heating equipment with a combined input rating less than or equal to 150,000 Btu/hr is not required to be provided with air from outdoors. However, the air volume within the space shall comply with the unconfined space definition for the aggregate input rating of all fuel-burning heating equipment and/or water heating equipment installed in that space. Fuel burning appliances typically used on an intermittent basis, such as clothes dryers, residential cooking equipment, and/or fireplaces are not required to be provided with air from outdoors. However, the combined air volume within the adjacent, communicating living spaces (not including bedrooms, bathrooms, and toilet rooms) shall comply with the unconfined space definition for the aggregate input rating of all fuel burning appliances installed in those living spaces.

Municipal Code of Chicago § 18-28-703.1 Confined spaces.

18-28-703.1 Confined spaces. Fuel burning space heating and/or water heating equipment with a combined input rating greater than 150,000 Btu/hour shall be provided with air from outdoors for combustion and dilution using the methods described in Section 18-28-703.3. (Amend Coun. J. 11-9-16, p. 36266, § 36) Exception: Single-family and two-family dwellings (including townhouses) are not required to use outdoor air for combustion and dilution. Such dwellings shall be provided with air for combustion and dilution in accordance with Sections 18-28-702, 18-28-703.2, or 18-28-703.3. Fuel burning heating and/or water heating equipment with a combined input rating less than or equal to 150,000 Btu/hr shall be provided with air for combustion and dilution in accordance with Sections 18-28-703.2 or 18-28-703.3. Fuel burning appliances typically used on an intermittent basis, such as clothes dryers, residential cooking equipment, and/or fireplaces shall be provided with air for combustion and dilution in accordance with Section 18-28-703.2.

Municipal Code of Chicago § 18-28-703.2 Indoor air.

18-28-703.2 Indoor air. The confined space shall be provided with two permanent openings communicating directly with other spaces of sufficient volume so that the combined volume of all such spaces meets the criteria for an unconfined space. The total input of all fuel burning equipment installed in the combined spaces shall be used to determine the required minimum volume. Each opening shall have a minimum free area of not less than 1 in. 2 /1,000Btu/hr (2120 mm 2 /kW) of the total input rating of all fuel burning equipment in the confined space, but not less than 100 in. 2 (0.06 m 2 ). One opening shall be within 12 in. (300 mm) of the top of the enclosure, and one opening shall be within 12 in. (300 mm) of the bottom of the enclosure. The minimum dimension of air openings shall be not less than 3 in. (8 cm).

Municipal Code of Chicago § 18-28-703.3 Outdoor air.

18-28-703.3 Outdoor air. All air from outdoors. The confined space shall communicate with the outdoors in accordance with methods 1 or 2, which follow. The minimum dimension of air openings shall be not less than 3 in. (80 mm). If ducts are used, the ducts shall be of the same cross- sectional area as the free area of the openings to which they connect. 1. Two permanent openings, one commencing within 12 in. (300 mm) of the top of the enclosure and one commencing within 12 in. (300 mm) of the bottom of the enclosure shall be provided. The openings shall communicate directly, or by ducts, with the outdoors or with attic spaces that freely communicate with the outdoors. (a) If directly communicating with the outdoors or if communicating to the outdoors through vertical ducts, each opening shall have a minimum free area of 1 in. 2 per 4000 Btu/hr (550 mm 2 /kW) of the total input rating of all equipment in the enclosure. (b) If communicating with the outdoors through horizontal ducts, such opening shall have a minimum free area of not less than 1 in. 2 per 2000 Btu/hr (1100 mm 2 /kW) of the total input rating of all equipment in the enclosure. 2. One permanent opening commencing within 12 in. (300 mm) of the top of the enclosure, shall be permitted if the equipment has clearances of at least 1 in. (25 mm) from the sides and back and 6 in. (160 mm) from the front of the appliance. The opening shall directly communicate with the outdoors or shall communicate with the outdoors through a vertical or horizontal duct or space that freely communicate with the outdoors. The opening shall have a minimum free area as follows: (a) 1 in. 2 /3000 Btu/hr (700 mm 2/ kW) of the total input rating of all equipment located in the enclosure, and (b) Not less than the sum of the areas of all vent connectors in the confined spaces.

Municipal Code of Chicago § 18-28-705.1

18-28-705.1 Engineered combustion air installations shall provide an adequate supply of combustion and dilution air and shall be approved by the authority having jurisdiction.

Municipal Code of Chicago § 18-28-706.1 Mechanical combustion air supply for oil-fired appliances.

18-28-706.1 Mechanical combustion air supply for oil-fired appliances. Where all combustion air and dilution air is provided by a mechanical forced-air system, the combustion air and dilution air shall be supplied at the minimum rate of 1 cfm per 2,400 Btu/h [0.00067 m 3 /(s x kW)] of combined input rating of all the fuel-burning appliances served. Each of the appliances served shall be electrically interlocked to the mechanical forced-air system so as to prevent operation of the appliances when the mechanical system is not in operation. Where combustion air and dilution air is provided by the building's mechanical ventilation system, the system shall provide the specified combustion/dilution air rate in addition to the required ventilation air.

Municipal Code of Chicago § 18-28-706.2 Mechanical combustion air supply for gas-fired appliances.

18-28-706.2 Mechanical combustion air supply for gas-fired appliances. Where all combustion air is provided by a mechanical air supply system, the combustion air shall be supplied from outdoors at the minimum rate of 0.35 ft 3 /min per 1,000 Btu/hr (0.034 mm 3 /kW) for all appliances located within the space.

Municipal Code of Chicago § 18-28-706.2.2

18-28-706.2.2 Each of the appliances served shall be interlocked to the mechanical air supply system to prevent main burner operation where the mechanical air supply system is not in operation.

Municipal Code of Chicago § 18-28-706.2.3

18-28-706.2.3 Where combustion air is provided by the building's mechanical ventilation system, the system shall provide the specified combustion air rate in addition to the required ventilation air.

Municipal Code of Chicago § 18-28-707.1 General.

18-28-707.1 General. Fuel-burning appliances that are listed and labeled for direct combustion air connection to the outdoors shall be installed in accordance with the manufacturer's installation instructions.

Municipal Code of Chicago § 18-28-708.1 General.

18-28-708.1 General. Combustion air ducts shall: 1. Be of galvanized steel complying with Chapter 6 or of equivalent corrosion-resistant material approved for this application. Exception: Within dwelling units, unobstructed stud and joist spaces shall not be prohibited from conveying combustion air, provided that not more than one required fireblock is removed. 2. Have a minimum cross-sectional dimension of 3 inches (76 mm). 3. Terminate in an unobstructed space allowing free movement of combustion air to the appliances. 4. Have the same cross-sectional areas as the free area of the openings to which they connect. 5. Serve a single appliance enclosure. 6. Not serve both upper and lower combustion air openings where both such openings are used. The separation between ducts serving upper and lower combustion air openings shall be maintained to the source of combustion air. 7. Not be screened where terminating in an attic space. 8. Not slope downward toward the source of combustion air, where serving the upper required combustion air opening.

Municipal Code of Chicago § 18-28-709.1 General.

18-28-709.1 General. The required size of openings for combustion and dilution air shall be based on the net free area of each opening. The net free area of an opening shall be that specified by the manufacturer of the opening covering. In the absence of such information, openings covered with metal louvers shall be deemed to have a net free area of 75 percent of the area of the opening, and openings covered with wood louvers shall be deemed to have a net free area of 25 percent of the opening.

Municipal Code of Chicago § 18-28-709.2 Dampered openings.

18-28-709.2 Dampered openings. Where the combusting air openings are provided with volume, smoke or fire dampers, the dampers shall be electrically interlocked with the firing cycle of the appliances served, so as to prevent operation of any appliance that draws combustion and dilution air from the room when any of the dampers are closed. Manually operated dampers shall not be installed in combustion air openings.

Municipal Code of Chicago § 18-28-710.1 General.

18-28-710.1 General. Combustion air openings to the outdoors shall comply with the location and protection provisions of Sections 18-28-401.5 and 18-28-401.6 applicable to outside air intake openings.

Municipal Code of Chicago § 18-28-711.1 General.

18-28-711.1 General. Carbon monoxide detection shall be provided as required in Section 915 of the Chicago Building Code. (Amend Coun. J. 4-10-19, p. 100029, Art. XII, § 13; Amend Coun. J. 9-14-21, p. 35949, Art. VII, § 2)
Source: City of Chicago, Municipal Code of Chicago (American Legal Publishing, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/chicago/latest/chicago_il/0-0-0-2687676Fetched: 10/24/2026

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