Okla. Admin. Code § 748:20-10-10
Chapter 4 of the Oklahoma adopted NEC® 2023 is adopted with the following modification: Section 422.16(B)(5) Gas-fired central furnaces. This section has been added to allow flexible cord-and-plug connections in dwelling units as an alternative means of temporarily supplying the gas-fired furnace by a portable generator for heating purposes. The change also specifies the maximum length of the cord. This section has been added to read: 422.16(B)(5) Gas-fired central furnaces. Gas-fired furnaces supplying dwelling units shall be permitted to be connected by a flexible cord-and-plug. The flexible cord shall have an equipment grounding conductor and be terminated into a grounding-type attachment plug. The cord and attachment plug shall have sufficient ampacity for the load, and shall be routed or otherwise protected to prevent physical damage to the cord or attachment plug. The cord length shall not be greater than 9 feet.
Okla. Admin. Code § 748:20-10-10