A fire-fighting system including: a pressurized gas supply; a vessel for storing a solution of water and a foaming agent, the vessel being connected to the pressurized gas supply for pressurizing the vessel in use; and a mixer for mixing gas from the pressurized gas supply with the solution to generate foam, wherein the mixer includes: a solution inlet for receiving the solution from the vessel; a foam outlet; one or more injection ports connected to the pressurized gas supply for injecting gas bubbles into the solution to form a mixture of the solution and the gas bubbles; and a foaming chamber extending between the solution inlet and the foam outlet, the mixture flowing through the foaming chamber to generate foam at the foam outlet, at least one internal surface of the foaming chamber including a shearing structure for shearing the gas bubbles as the mixture flows through the foaming chamber.