Okla. Admin. Code § 748:20-6-15
Chapter 10 of the IRC® 2018 is adopted with the following modification: Section R1005.7 Factory-built chimney offsets. This section has been modified to provide an exception for listed and labeled factory-built chimneys that are part of a fireplace and chimney assembly to be installed according to the manufacturer's installation instructions. This section has been modified to read: R1005.7 Factory-built chimney offsets. Where a factory-built chimney assembly incorporates offsets, no part of the chimney shall be at an angle of more than 30 degrees (0.52 rad) from vertical at any point in the assembly and the chimney assembly shall not include more than four elbows. Exception: Where chimneys are part of a listed and labeled factory-built fireplace they may be installed in accordance with the fireplace and chimney manufacturer's installation instructions.
Okla. Admin. Code § 748:20-6-15