The Acceptable Separation Distances (ASD) regulations, 24 CFR part 51, Subpart C, provide the technical requirements for determining ASD from HUD-assisted projects in proximity to hazardous operations of conventional fuels or chemicals of an explosive or flammable nature, including propane. These regulations were developed in 1984 and need to be updated to conform to industry standards that reduce restrictions on residential propane tanks. This proposed rule would allow for unmitigated residential propane tanks that are up to 250 gallons, in compliance with Code 58 of the National Fire Protection Association and are designed, fabricated, tested and marked or stamped according to the regulations of the U.S. Department of Transportation (DOT); the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Rules for the Construction of Unfired Pressured Vessels, Section VIII; or the American Petroleum Institute (API)-ASME Code for Unfired Pressure Vessels for Petroleum Liquids and Gases.  These standards were not in place when the regulation was developed in 1984.