REFLEAK estimates composition changes of zeotropic mixtures in leak and recharge processes. The leak/recharge simulation program consists of three parts: 1) the pre-processing section for inputting required data, 2) the computation section which simulates leak/recharge processes and, 3) the post-processing section to display calculated results and to print or store data and graphs. Version 4.0 System Requirements: Free space for complete installation: 10 MB. REFLEAK is designed to run on any personal computer (PC) capable of running Microsoft Windows 7, XP with Service Pack 3, and Vista operating systems. The installation module requires .NET Framework 2.0 Service Pack 2 (or later version), which can be downloaded from the Microsoft website if not present on the user's PC.