RSPA is amending the Hazardous Materials Regulations (HMR; 49 CFR parts 171-180) to regulate materials which pose a hazard due to their being offered for transportation or transported at elevated temperatures. Included are materials in a liquid phase having temperatures at or above 100 'C (212 *F) and materials in a solid phase having temperatures at or above 240 °C (464 'F). RSPA is also regulating, as flammable liquids, materials in a liquid phase with flash points at or above 37.8 'C (100 'F) which are intentionally heated and offered for transportation or transported in bulk quantities at or above their flash points. The intended effects of these regulatory changes are to communicate the hazards of these elevated temperature materials by means of marking, shipping papers and placarding, and to prescribe packaging requirements for these materials. The changes are necessary to alert the public and emergency response personnel to the risks posed by these materials and to specify minimum levels of packaging for them in order to minimize the possibility of their unintentional release.