Currently the natural materials become popular building material for houses, buildings and recreational property. The risk of fi res in residential timber construction or eco houses cannot be completely ruled out, therefore there is a need for proper and correct implementing preventive measures and application of all available solutions, which may reduce the risk of fi re as far as possible, to slow down the combustion process, to protect the life of people, animals and also the building itself until arrival members of the Fire and Rescue Services. Fireproofi ng of combustible materials is a specifi c area of fi re protection. For scientifi c research as well as for real-life practice, not only their structural and physical properties, but also fi re-technical characteristics are really important. The present researchers mostly focus on fi re-retardant treatment of wood that is why the authors of this contribution focused on a different combustible material. This research article presents the experimental testing and examination of the reaction to fi re test of the selected thermal insulation of hemp fi ber that was impregnated by the selected fi re retardant in laboratory conditions