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Gypsum ducts.

Municipal Code of Chicago § 18-28-603.4.1
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18-28-603.4.1 Gypsum ducts. Gypsum boards that form air shafts (ducts) shall be limited to vertical return shafts where the air temperatures do not exceed 125°F (52°C) and the gypsum board surface temperature is maintained above the air stream dew point temperature.
Source: City of Chicago, Municipal Code of Chicago (American Legal Publishing, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/chicago/latest/chicago_il/0-0-0-2687582Fetched: 10/24/2026

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18-28-603.4.1 | Corpus