Methods of and systems for filtering particles, whose largest cross-sectional dimension is greater than a predetermined distance, of a multiphase fluid that comprises a particulate phase are provided. The methods provide for a step for delivering the multiphase flowable fuel through filter means, wherein the filter means is for retaining particles of the particulate phase whose largest cross-sectional dimension is greater than a predetermined distance. The systems provide for means for retaining particles whose largest cross-sectional dimension is greater than a predetermined distance, and means for providing at least one flow path for at least part of the multiphase fluid. In one application, the methods and systems are used in connection with an electrochemical power source and components thereof.