Full discharge tests used in verification and quality assurance of total flooding Halon 1301 fire protection systems represent a large portion of the Halon 1301 emissions annually. It is, therefore, desirable to use a suitable simulant in these tests in view of the stratospheric ozone problem and current and future regulation of Halon 1301. Sulfur hexafluoride, SF6, and chlorodifluoromethane, R-22, were identifed as candidate simulants on the basis of their similarity in physical properties to Halon 1301. These two candidates were then evaluated on the basis of leakage from an enclosure. SF6 was determined to be an excellent simulant for Halon 1301 when considering leakage from an enclosure. Further testing of SF6 and R-22 is progressing on other important aspects of Halon 1301 systems; i.e., flow hydraulics and initial mixing.