Link: http://adteputek.com/b2evolution/blog2.php/2009/09/17/ectfe-films-have-better-flame-retardancy

ECTFE Films have a higher LOI "Limiting Oxygen Index" than ETFE Films therefore higher flamability ratings. The Limiting Oxygen Index (LOI) test is a widely used research and quality control tool for determining the relative flammability of polymeric materials. A numerical index, the ‘LOI’, is defined as the minimum concentration of oxygen in an oxygen – nitrogen mixture, required to just support downward burning of a vertically mounted test specimen. Hence, higher LOI values represent better flame retardancy.