The fight for a healthy and clean climate forces many restrictive changes to European law. Wooden construction fits very well into these changes, as it is able to store carbon dioxide for years. Unfortunately, many regulations, e.g. fire regulations, still hinder the development of this type of structures in Poland. Wooden elements used that have class D must achieve class B of fire resistance. For this purpose, they are modified with flame retardant agents. Three salt flame retardants based on: 1-phosphorus and iron, 2-phosphorus and nitrogen and 3-ogranic componds including benzoates, were used in the tests. The amount of applied fire retardants was compared depending on the impregnation technology used: surface immersion and pressure, as well as the reaction to fire of impregnated wooden elements. As a result of the tests, no impregnation used improved the fire properties, as shown by a small-scale cone calorimeter test. The project results indicate the need to conduct new basic research on the possibility of permanently improving the fire properties of wooden elements, which would allow the widespread use of wood in construction.