The invention relates to a compressed air foam producer, wherein a fire or decontamination specific additive is injected directly into the foam forming flow supplied to the main water flow and/or the main water flow. A mixing pump for the foaming agent draws off an auxiliary and motive water flow, wherein initially the additive and then the foaming agent is injected. The foaming agent-additive-water mixture, which is produced directly on site, is mixed well together and with the main water flow ensuring a fine, uniform distribution of the additives in the compressed air foam. The thus produced compressed air foam ensures optimal, economical and environmentally friendly fire-fighting and decontamination.