Method for sanitizing surfaces intended to be passed over by the air, in particular air ducts and duct components, which comprises the following operating steps: • a step for preparing a first dose of an epoxy polymer suitable for being diluted in water; • a step for preparing a second dose of a crosslinking catalyst; • a step for mixing the first dose of said epoxy polymer with the second dose of said crosslinking catalyst, obtaining a mixture in liquid phase with filming effect; • at least one step for spreading said liquid mixture with filming effect on a surface to be treated, intended to be passed over by the air; • at least one crosslinking step during which said liquid mixture with filming effect polymerizes and crosslinks, forming a crosslinked solid coating; - characterized in that said catalyst is selected from the family of polyamines and said second dose thereof is prepared in an amount greater than that required stoichiometrically for crosslinking of the first dose of said epoxy polymer; - characterized in that said step of spreading said liquid mixture with filming effect on said surface to be treated forms a substantially uniformly spread and continuous film of liquid mixture with filming effect, which impregnates the contaminants present on the surface and thus defines a first microbicidal step for a period of time, preceding said crosslinking step, during which said film remains substantially liquid and during which said polyamines contained in said film act on the contaminants present on said surface to be treated, eliminating any microbes present therein; - and characterized in that said crosslinked solid coating defines a second microbicidal step, during which free surface amine groups of the polyamines which have not chemically bonded with the epoxy polymers, prevent the formation of microbial content, the presence of said free amine groups on the surface of the coating being ensured by the introduction of the polyamines into the mixture containing the epoxy precursors in hyperstoichiometric amounts. • a step for preparing a first dose of an epoxy polymer suitable for being diluted in water; • a step for preparing a second dose of a crosslinking catalyst; • a step for mixing the first dose of said epoxy polymer with the second dose of said crosslinking catalyst, obtaining a mixture in liquid phase with filming effect; • at least one step for spreading said liquid mixture with filming effect on a surface to be treated, intended to be passed over by the air; • at least one crosslinking step during which said liquid mixture with filming effect polymerizes and crosslinks, forming a crosslinked solid coating; - characterized in that said catalyst is selected from the family of polyamines and said second dose thereof is prepared in an amount greater than that required stoichiometrically for crosslinking of the first dose of said epoxy polymer; - characterized in that said step of spreading said liquid mixture with filming effect on said surface to be treated forms a substantially uniformly spread and continuous film of liquid mixture with filming effect, which impregnates the contaminants present on the surface and thus defines a first microbicidal step for a period of time, preceding said crosslinking step, during which said film remains substantially liquid and during which said polyamines contained in said film act on the contaminants present on said surface to be treated, eliminating any microbes present therein; - and characterized in that said crosslinked solid coating defines a second microbicidal step, during which free surface amine groups of the polyamines which have not chemically bonded with the epoxy polymers, prevent the formation of microbial content, the presence of said free amine groups on the surface of the coating being ensured by the introduction of the polyamines into the mixture containing the epoxy precursors in hyperstoichiometric amounts. - characterized in that said catalyst is selected from the family of polyamines and said second dose thereof is prepared in an amount greater than that required stoichiometrically for crosslinking of the first dose of said epoxy polymer; - characterized in that said step of spreading said liquid mixture with filming effect on said surface to be treated forms a substantially uniformly spread and continuous film of liquid mixture with filming effect, which impregnates the contaminants present on the surface and thus defines a first microbicidal step for a period of time, preceding said crosslinking step, during which said film remains substantially liquid and during which said polyamines contained in said film act on the contaminants present on said surface to be treated, eliminating any microbes present therein; - and characterized in that said crosslinked solid coating defines a second microbicidal step, during which free surface amine groups of the polyamines which have not chemically bonded with the epoxy polymers, prevent the formation of microbial content, the presence of said free amine groups on the surface of the coating being ensured by the introduction of the polyamines into the mixture containing the epoxy precursors in hyperstoichiometric amounts.