NFPA 54 National Fuel Gas Code Practice Test

CSST must be supported according to its listed method. When CSST on a roof isn’t installed with a listed support, the code caps the length that can remain unsupported at 30 inches. This limit helps control movement from wind, roof motion, and temperature changes, reducing stress on fittings and the gas system.

Shorter unsupported spans are allowed, but they are not the maximum—the question asks for the maximum. A length of 60 inches would exceed the allowed limit, so it’s not permitted. Therefore, the maximum allowable unsupported length on a roof top is 30 inches.