AbstractEffects of the impregnation materials borax, boric acid, and Tanalith-E on combustion properties of Oriental beech (Fagus orientalis Lipsky) were investigated. The immersion method was used for long-term impregnation (24 h). After the impregnation process, polyurethane as well as synthetic, acid hardening, and water-based varnishes were applied on the wood sample surfaces according to company’s suggests. The combustion test was performed according to the ASTM-E 69 standard. The mass reduction, release of gasses (CO, NO, O2), and the temperature differences of samples were determined for each 30 seconds during combustion. It was shown that the most mass reduction occurred when both polyurethane varnish and boric acid were applied.