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    Mechanical / HVAC Code Adoption

    Illinois Mechanical / HVAC Code: IMC 2021

    Illinois follows IMC 2021 as the basis for mechanical / hvac work. Permits and inspections are issued by the local Authority Having Jurisdiction (AHJ), which may publish additional amendments.

    Adoption details

    Model code family
    IMC / UMC
    Adopted edition
    IMC 2021
    Last verified
    2026-05-29

    Note: Mechanical-code edition usually tracks the state plumbing-code family — verify with local AHJ.

    Related resources for Illinois

    Frequently Asked Questions

    What mechanical / hvac code does Illinois use?

    Illinois currently follows IMC 2021 for mechanical / hvac work. Always confirm the in-force edition with the local Authority Having Jurisdiction (AHJ) — county or city amendments can apply.

    Do I need a permit for mechanical / hvac work in Illinois?

    Most mechanical / hvac work in Illinois — including new installations, system replacement, and gas-fueled appliance hookups — requires a permit from the local building department and an inspection at completion. Homeowner permits are typically allowed for owner-occupied residences; commercial work requires a licensed contractor.

    Where do I check Illinois mechanical / hvac code amendments?

    Local jurisdictions (city or county) often publish amendments on the state's building-codes board website or in the municipal code. The current IMC 2021 text is published by its model-code body (ICC, IAPMO, or NFPA depending on the trade).

    Are there any unusual mechanical / hvac requirements in Illinois?

    Mechanical-code edition usually tracks the state plumbing-code family — verify with local AHJ.

    Reference guidance only — adoption editions and local amendments vary by city or county. Always confirm requirements with your local Authority Having Jurisdiction (AHJ) before designing, permitting, or constructing.

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