The U.S. Department of Homeland Security (DHS) Science and Technology Directorate (S&T) CSAC led the Jack Rabbit project of large-scale outdoor chlorine release trials, with a collaborative team of partners and cosponsors from government, industry and academia. These field trials and follow-on studies filled critical data gaps for toxic inhalation hazard (TIH) chemical release modeling and emergency response procedures. Phase 1 was completed in September of 2015, with the execution of five chlorine release trials ranging from five to 10 tons. Phase 2 was completed in September of 2016, with four additional chlorine release trials ranging from 10 to 20 tons each.