M.B.srl F50BE-F50BEMED Marine Approved 50 Liter Foam Fire Extinguisher a perfect solution for initial fires of fire classes A and B are these easily manageable foam extinguishers. Due to the low specific density, the water film-forming foam agents are able to compose a sealed steam-tight aqueous layer on the surface of fire, even with burning liquids. This barrier prevents vapors and gases from escaping and stops the oxygen supply to the burning material. In this way, the fire is choked. In addition, the foam has a cooling effect thanks to its water content.