All AFFF firefighting agents contain fluorinated surfactants (fluorosurfactants). They are key ingredients that provide AFFF with the required low surface tension (15 to 17 mN/m) and positive spreading coefficient that enables film formation on top of lighter fuels. It is this film formation capability that gives AFFF its name and its effectiveness against flammable liquid fires. The chemicals used to produce fluorosurfactants can be manufactured by different processes and have different chemical structures.