The installation of gas engines shall be in accordance with NFPA 37. [NFPA 54:10.24]
Stationary gas engines shall not be rigidly connected to the gas supply piping. [NFPA 54:10.24.1]
Stationary engine generators shall be tested in accordance with UL 2200, and shall be installed in accordance with NFPA 37 and the manufacturer's installation instructions.