This notice proposes regulations to control the concentration of hydrogen sulfide (II2S in natural gas pipeline systems because high concentrations of HS are extremely toxic if released. The proposed rule would: (a) Prohibit operators from transporting in a transmission line downstream of gas processing plants, sulfur recovery plants, or storage fields, natural gas containing more than 1 grain of hydrogen sulfide (H2S) per 100 standard cubic feet (SCF) of natural gas; (b) Require that the release of H2S in excess of 20 grains per 100 SCF of natural gas into a transmission line be telephonically reported to DOT; and (c) Require that onshore and offshore gathering lines carrying H2S in excess of 31 grains per 100 SCF of natural gas have a contingency plan in case of the release of the gas into the atmosphere.