Process for producing polyurethane foams by reacting a component comprising a) at least one compound which comprises isocyanate reactive hydrogen atoms, b) water and/or physical blowing agent, c) auxiliary and additive substances, d) at least one halogen-free flame retardant comprising d.1) a phosphoric ester of formula in which m is an integer from 1 to 3, R 1, R 2, R 3, R 4, R 5 each independently represent H, a C 6 - to C 12 -aryl radical, a C 2 H 2 Ph radical ("styryl"), an O-alkyl radical having C 1 to C 5 -carbon atoms, an O-aryl radical having C 6 to C 12 -carbon atoms and/or COOR 11 where R 11 = C 1 - to C 5 -alkyl radical, and wherein at least one of the radicals R 1, R 2, R 3, R 4, R 5 is distinct from H; or d.2) a phosphoric ester of formula in which n is an integer from 1 to 4, R 6, R 7, R 8, R 9, R 10 each independently represent H, a straight-chain, branched or cyclic C 1 - to C 10 -alkyl radical, a C 6 - to C 12 -aryl radical, a C 2 H 2 Ph radical ("styryl"), an O-alkyl radical having C 1 to C 5 -carbon atoms, an O-aryl radical having C 6 to C 12 -carbon atoms and/or COOR 11 where R 11 = C 1 - to C 5 -alkyl radical, with e) at least one di- and/or polyisocyanate, wherein the mixture is free from halogen-containing flame retardants. a) at least one compound which comprises isocyanate reactive hydrogen atoms, b) water and/or physical blowing agent, c) auxiliary and additive substances, d) at least one halogen-free flame retardant comprising d.1) a phosphoric ester of formula in which m is an integer from 1 to 3, R 1, R 2, R 3, R 4, R 5 each independently represent H, a C 6 - to C 12 -aryl radical, a C 2 H 2 Ph radical ("styryl"), an O-alkyl radical having C 1 to C 5 -carbon atoms, an O-aryl radical having C 6 to C 12 -carbon atoms and/or COOR 11 where R 11 = C 1 - to C 5 -alkyl radical, and wherein at least one of the radicals R 1, R 2, R 3, R 4, R 5 is distinct from H; or d.2) a phosphoric ester of formula in which n is an integer from 1 to 4, R 6, R 7, R 8, R 9, R 10 each independently represent H, a straight-chain, branched or cyclic C 1 - to C 10 -alkyl radical, a C 6 - to C 12 -aryl radical, a C 2 H 2 Ph radical ("styryl"), an O-alkyl radical having C 1 to C 5 -carbon atoms, an O-aryl radical having C 6 to C 12 -carbon atoms and/or COOR 11 where R 11 = C 1 - to C 5 -alkyl radical, with d.1) a phosphoric ester of formula in which m is an integer from 1 to 3, R 1, R 2, R 3, R 4, R 5 each independently represent H, a C 6 - to C 12 -aryl radical, a C 2 H 2 Ph radical ("styryl"), an O-alkyl radical having C 1 to C 5 -carbon atoms, an O-aryl radical having C 6 to C 12 -carbon atoms and/or COOR 11 where R 11 = C 1 - to C 5 -alkyl radical, and wherein at least one of the radicals R 1, R 2, R 3, R 4, R 5 is distinct from H; or m is an integer from 1 to 3, R 1, R 2, R 3, R 4, R 5 each independently represent H, a C 6 - to C 12 -aryl radical, a C 2 H 2 Ph radical ("styryl"), an O-alkyl radical having C 1 to C 5 -carbon atoms, an O-aryl radical having C 6 to C 12 -carbon atoms and/or COOR 11 where R 11 = C 1 - to C 5 -alkyl radical, and wherein at least one of the radicals R 1, R 2, R 3, R 4, R 5 is distinct from H; or d.2) a phosphoric ester of formula in which n is an integer from 1 to 4, R 6, R 7, R 8, R 9, R 10 each independently represent H, a straight-chain, branched or cyclic C 1 - to C 10 -alkyl radical, a C 6 - to C 12 -aryl radical, a C 2 H 2 Ph radical ("styryl"), an O-alkyl radical having C 1 to C 5 -carbon atoms, an O-aryl radical having C 6 to C 12 -carbon atoms and/or COOR 11 where R 11 = C 1 - to C 5 -alkyl radical, n is an integer from 1 to 4, R 6, R 7, R 8, R 9, R 10 each independently represent H, a straight-chain, branched or cyclic C 1 - to C 10 -alkyl radical, a C 6 - to C 12 -aryl radical, a C 2 H 2 Ph radical ("styryl"), an O-alkyl radical having C 1 to C 5 -carbon atoms, an O-aryl radical having C 6 to C 12 -carbon atoms and/or COOR 11 where R 11 = C 1 - to C 5 -alkyl radical, e) at least one di- and/or polyisocyanate, wherein the mixture is free from halogen-containing flame retardants.