Wood-based materials such as OSB-board are increasingly used in construction. It is a composite and combustible material that needs to be protected from fire. The diploma thesis will be an experimental follow-up to the bachelor thesis, where the influence of natural aging, changing concentration/ratio and changing climatic conditions (at defined time intervals)on the effect of the retardant and on the change of fire protection properties of the protected OSB board will be observed. The diploma thesis is divided into a practical and theoretical part. The theoretical part focuses on summary of knowledge on wood-based materials, the methods of their fire protection and also the description of protective substances. The practical part examines the effect of two protective substances with flameretardant effect (HR-Prof) and with fungicidal-insecticidal effect (Krovsan), which were applied in different ratios. The thesis presents the findings that were achieved in the experiments performedin the time interval of two and a half years.