In this study, the determination of the burning characteristics of oriented strandboard (OSB) and the effect on the burning characteristics of OSB when three chemical substances, potassium carbonate, borax and wolmanit, which are used as a fire retardant, are applied with the methods of brushing or dipping, have been researched. A total of 56 each samples were prepared for this purpose in accordance with DIN 4102 and subjected to the burning test. According to the statistical analyses obtained as the result of the test, potassium carbonate was determined to be the most suitable substance for improving the burning characteristics of the OSB within the existing substances due to the fact that it had the longest ignition time and the shortest periods of burning with flames and as embers along with borax after the flames were turned off. The most suitable method of applying the chemical substances to the surface is the dipping method because it extends the ignition time of the OSB and has a shortening effect on the periods of the burning with flames and as embers after the flame has been turned off. (c) 2006 Elsevier Ltd. All rights reserved.