Current aircraft fire suppression bottles for dry bay and engine nacelle applications, which are designed to meet Military Specification MIL-C-22284A (proof pressure of 9.62 MPa and minimum burst pressure of 12.37 MPa), are normally filled with liquid halon 1301 (CF 3 Br) to about half of the bottle volume, and the bottle is then pressurized with nitrogen to a specified equilibrium pressure at room temperature. The purpose of using the pressurization gas is to expedite the discharge of the agent and to facilite the dispersion of the agent. Without nitrogen pressurization, the bottle pressure can be low at extremely cold ambience that there is virtually no driving force to exepl the agent from the bottle in case of a fire, thus hindering a rapid release of the mixture. Three important issues have emerged and need be considered when a halon alternative as an in-flight fire suppressant : (1) the system hardware, (2) the thermophysical properties of the agent/nitrogen mixture, and (3) the agent/nitrogen mixture behavior during a discharge. In this section, the last two issues which are pertinent to agent storage and its subsequent discharge will be addressed in detail. The results obtained from this study provide important technical information on bottle design and agent discharge for new generation aircraft that may use the halon alternatives, for the existing aircraft that may undergo retrofitting, or simply for possible drop-in replacements.