Wood preservatives have been widely used to extend the service life of wood. The aim of this study is to evaluate the effects of various wood preservatives with different chemical loadings on fire performance of treated fir wood using by oxygen index test technique (ASTM D 2863-6). The limiting oxygen index (LOI) is the minimum percentage oxygen that is required to continue flaming combustion of a sample under laboratory conditions. For this purpose; wood preservatives commonly used in wood protection industry including amine-copper-quaternary, tanalith-E, wolmanit-CB, imersol aqua, vacsol aqua, timbercare aqua and protim-418 were studied as wood preservative chemicals. Mixture of boric acid + borax was also used as reference sample. The results indicated that LOI levels of all treated fir wood samples were higher than that of control samples except for timbercare aqua and protim-418 treated samples. The highest LOI level was obtained within 5% of wolmanit-CB and 2% of boric acid + borax treated wood samples. It appears that more than 3% concentration of wolmanit-CB treatment may have a potential fire retardant. (C) 2014 Elsevier Ltd. All rights reserved.