The main component of plastics are polymers, which despite numerous advantages also entail certain drawbacks. The least desired features of polymers comprise the low thermal stability and flammability, which in turn depend on chemical and physical changes taking place in the polymer at a high temperature. To minimise their adverse properties, various research works are being carried out to study the present and new polymer groups, including also polyurethanes, large amounts of which are manufactured in the form of foam materials and raw materials needed in the manufacturing of production plants all over Poland. Poland is currently in the group of major foam material manufacturers in Europe. Currently research works are oriented at enhancing durability, rigidity, insulating power and fire resistance of diverse plastics, including also polyurethanes, and limiting the costs of their production. The objective of the study is to define values of oxygen indices of selected polyurethane materials at ambient temperature and at elevated temperature, and also to compare the impact of modifiers on flammability of polyurethanes for non-modified samples.