Abstract: A composite yarn includes a core composed of a continuous yarn, and a coated sheath composed of a matrix including at least one chlorinated polymer material, and a fire-retarding filler incorporated into and distributed within said matrix, wherein, in combination, the fire-retarding filler comprises a ternary composition which combines an oxygenated antimony compound, a hydrated metal oxide, the metal of which is chosen from aluminum, magnesium, tin, zinc and lead, and a zinc borate and, together with said ternary composition, the total weight content of inorganic matter in the yarn is between 4% and 65%.