Combustible properties of treated douglas wood specimens and fire-retardancy of some preservatives were tested in this study. Crib test of ASTM E 160-150 was followed. Results indicated that, aqueous solutions of boric acid (BA), borax (Bx) (Na2BO7 10H2O) or BA + Bx mixture (7: 3, w: w) had fire retardant efficacy (FRE) over untreated wood and reduced the combustibility of vinil monomers (Styrene and methylmetacrylate) which were applied as secondary treatment