The objective of this paper is to know the fire performance of wooden panels (Pinus radiata) impregnated with silica nanoparticles added to silica/alkali colloidal solutions. Two series of impregnated panels were prepared with diverse penetrations and retentions (a) after drying/curing the impregnants at laboratory conditions until reaching constant weight and (b) after finishing this stage with prior distiller water immersion for seven days and a later air exposition for attaining moisture balance. Panels were tested in a limiting oxygen chamber and in a two-foot tunnel. Some results displayed a high fire-retardant efficiency. Copyright © 2009 John Wiley & Sons, Ltd.