Abstract: A method for producing a fibrous fire protection agent composed of a fibrous material with boric acid particles adhering to its surface, by providing a mass of such fibrous material having a moisture content of up to 80 percent by weight, intimately mixing in a mixer that mass of material with a quantity of powdered boron mineral material, spraying a quantity of concentrated sulfuric acid into the mixer during the mixing step to form a granulate, feeding the resulting granulate onto an evaporation line, and withdrawing the granulate from the evaporation line and comminuting the granulate in an impact pulverizer to form it into the fibrous fire protection agent.