This European Technical Specification describes the characteristics which fire-retardant treated wood products should exhibit so that their fire-retardant properties persist undiminished throughout the desired service life in the anticipated conditions of use. The Technical Specification prescribes the classification requirements for the durability of the reaction to fire performance of fire-retardant treated wood-based products to be used in interior and exterior end use conditions. The products initially need to meet required reaction to fire classification. For interior and exterior use, limited hygroscopicity needs to be verified. In addition, products for exterior use needs to meet the minimum durability of reaction to fire performance requirements specific to the end use. The requirements are applicable for fire-retardant treated (applied by penetrating and superficial processes or with film forming or intumescent fire-retardant coatings) solid wood and wood-based products and woodbased products in which the fire-retardant is incorporated during manufacture. The fire-retardant treated products may be coated with an ordinary paint. Mechanical properties and biological durability of fire-retardant treated wood products are not covered by this European Technical Specification. Paints, coatings and varnishes intended to improve the reaction to fire performance of a construction product when incorporated in the works, i.e. a building, are covered by ETAG 028 . This Technical Specification may be used as a basis for an approval system.