Posted on April 4, 2013 by. Corrugated stainless steel tubing (CSST), is used to convey flammable gas inside or outside of a building. It is not mentioned in the 2011 NEC by name, but Informational Note No. 2 to 250.104(B) cites NFPA 54, the National Fuel Gas Code, as a source for additional information for gas piping systems. This document requires that CSST gas pipe to be bonded to the premises electrical grounding system.