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				FIRE PERFORMANCE OF WOOD PRODUCTS - At a Glance download complete document Combustibility and How Wood Burns Wood will burn when exposed to high enough temperatures and in the presence of oxygen. Thermal degradation of wood occurs in stages. The degradation process and the exact products of thermal degradation depend upon the rate of heating as well as temperatures. For wood in a fire:   • As the surface temperature of wood increases due to fire exposure, flammable vapors are produced and a char layer (burnt wood) is formed on the external surfaces. • In the presence of fire, these flammable vapors ignite and contribute to the fire. • As the char layer gets thicker, it insulates the remaining unburned wood and slows the rate of vapor production, thereby slowing the charring process. Flame Spread Lumber, plywood, and other wood-based materials, including the components of I-joists, and trusses, exhibit a relatively narrow range of flame spread. Flame spread rates for engineered wood products, suchas, laminated veneer lumber (LVL), parallel strand lumber (PSL) and laminated strand lumber (LSL) are within the same range as solid wood materials. Differences result from factors such as density, thickness, surface characteristics, and coatings or other chemicals applied, if any. Typically, at thicknesses greater than 1/4", flame spread is almost independent of material thickness. Charring Wood exposed to fire develops an insulating layer of char that further slows wood degradation. The char layer contributes no strength to the remaining cross-section, but acts to insulate the underlying wood from further charring, thus retarding the char rate. The structural capacity of a wood member exposed to fire depends upon its unburned-wood cross-section. Accordingly, char rate is a major factor in the determination of the fire endurance of wood products. Smoke Toxicity The major chemical elements found in natural wood products are carbon, hydrogen, and oxygen. When thermally decomposed, these elements primarily produce carbon monoxide, carbon dioxide, and water. Where nitrogen or halogens are present in significant quantities, the potential for production of hydrogen cyanide and hydrogen halide exists during the burning process. For more information on the fire performance of wood, click here to download the seven page PDF file.