The results of researches of wood burning parameters and influence of fire-retardant substances on them are given. Studies have shown that the process of heat insulation of a wooden structure is the formation of soot-like products on the surface of natural combustible material. Under the action of the burner flame on the protected sample treated with impregnating solutions based on a mixture of ammonium phosphate with antiseptic, the temperature of gaseous combustion products was 230 oC, and weight loss did not exceed 9%, while wood treated with a composition of urea and phosphoric acids and starch showed temperature of 160 oС with a weight loss of 3.6%. It is established that fire protection by coatings provides a low rate of burnout of wood samples and with increasing temperature exposure and translates into a non-flammable material that does not spread the flame on the surface.