Surfactants (surface active agents) in certain concentrations and combinations are known to have a harmful effect on filter/separators. They affect the basic physicochemical parameters associated with coalescence and the removal of solid particulate from hydrocarbon fuels. Tests conducted on military filter/separators indicate that JP-4 and JP-5 jet fuel can be decontaminated properly; however, problems exist in the decontamination of water from motor gasoline (MoGas) and No. 2 diesel fuel. Tests conducted to determine the effect of surfactants versus electrostatic charge generation indicate that small amounts of surfactants or combinations of surfactants and free water or solid particulates can convert a nearly inert fuel into a fuel producing high and dangerous levels of static electricity.