Fire extinguisher • with an extinguishing agent container for the extinguishing agent and a secondary container for a foaming agent, • with a extinguishing mixture channel, which is connected to the extinguishing agent container and in which the extinguishing mixture of extinguishing agent and foaming agent is expelled when using the fire extinguisher by pressurizing the extinguishing agent container by means of a propellant gas, • with a two-part mixing device, through which the extinguishing mixture is guided and which has: + a mixing chamber which is mounted on the end of the extinguishing hose connected to the extinguishing mixture channel, and + a ventilation chamber having a jacket which is constructed as a hollow cylindrical rotary body and which, on the one hand, is placed on the mouth of the mixing chamber and the mouth of which, on the other hand, serves as an extinguishing foam outlet through which the extinguishing mixture in the foamed state is sprayed as an extinguishing foam, • wherein the housing inner cross-section of the mixing chamber, in several radial planes, is filled by perforated plates (32, 33), which lie one behind the other in the flow, ∘ with the first perforated plate behind the extinguishing agent inlet, having a plurality of holes through which the extinguishing mixture flowing through is divided into a plurality of individual streams, ∘ and with the perforated plate following downstream • and wherein the ventilation chamber comprises, in a ventilation plane oriented as a radial cross-sectional plane, air inlet holes which ∘ are arranged on the circumference of the jacket, and ∘ directed into the interior of the mixing device, and ∘ which connect the interior of the jacket with the ambient air in such a way that sucked-in air jets are directed in the ventilation plane onto the extinguishing mixture divided into individual streams, • the inner cross-section of jacket of the ventilation chamber having a cross-sectional constriction between the aeration plane and said perforated plates, characterized in that the holes of the successive hole plates (32, 33) are not aligned and that the holes of the second hole plate have a direction different from the axial direction. • with an extinguishing agent container for the extinguishing agent and a secondary container for a foaming agent, • with a extinguishing mixture channel, which is connected to the extinguishing agent container and in which the extinguishing mixture of extinguishing agent and foaming agent is expelled when using the fire extinguisher by pressurizing the extinguishing agent container by means of a propellant gas, • with a two-part mixing device, through which the extinguishing mixture is guided and which has: + a mixing chamber which is mounted on the end of the extinguishing hose connected to the extinguishing mixture channel, and + a ventilation chamber having a jacket which is constructed as a hollow cylindrical rotary body and which, on the one hand, is placed on the mouth of the mixing chamber and the mouth of which, on the other hand, serves as an extinguishing foam outlet through which the extinguishing mixture in the foamed state is sprayed as an extinguishing foam, + a mixing chamber which is mounted on the end of the extinguishing hose connected to the extinguishing mixture channel, and + a ventilation chamber having a jacket which is constructed as a hollow cylindrical rotary body and which, on the one hand, is placed on the mouth of the mixing chamber and the mouth of which, on the other hand, serves as an extinguishing foam outlet through which the extinguishing mixture in the foamed state is sprayed as an extinguishing foam, • wherein the housing inner cross-section of the mixing chamber, in several radial planes, is filled by perforated plates (32, 33), which lie one behind the other in the flow, ∘ with the first perforated plate behind the extinguishing agent inlet, having a plurality of holes through which the extinguishing mixture flowing through is divided into a plurality of individual streams, ∘ and with the perforated plate following downstream ∘ with the first perforated plate behind the extinguishing agent inlet, having a plurality of holes through which the extinguishing mixture flowing through is divided into a plurality of individual streams, ∘ and with the perforated plate following downstream • and wherein the ventilation chamber comprises, in a ventilation plane oriented as a radial cross-sectional plane, air inlet holes which ∘ are arranged on the circumference of the jacket, and ∘ directed into the interior of the mixing device, and ∘ which connect the interior of the jacket with the ambient air in such a way that sucked-in air jets are directed in the ventilation plane onto the extinguishing mixture divided into individual streams, ∘ are arranged on the circumference of the jacket, and ∘ directed into the interior of the mixing device, and ∘ which connect the interior of the jacket with the ambient air in such a way that sucked-in air jets are directed in the ventilation plane onto the extinguishing mixture divided into individual streams, • the inner cross-section of jacket of the ventilation chamber having a cross-sectional constriction between the aeration plane and said perforated plates,