Although the fire resistance of wood depends on its dimensions, it needs a lot of time and energy to fire retard thick wood. On the other hand, it is easier and takes less time and energy to treat thin materials. The fire resistance of wood was improved by compressed treatment, even untreated wood, and moreover compressed wood loaded with chemicals was improved more. Fire resistance of a laminated board was the same as a solid compressed board, and also fire resistance of a laminated board which was arranged with compressed thin wood on two sides of untreated wood showed similar fire endurance. A laminated lathe veneer board showed better fire resistance than solid untreated wood and a laminated board with treated veneers arranged concentratively showed better fire resistance than it did when arranged dispersively.
So it was judged that it was important to retard fire ignition and to form a carbonized layer effectively in a fire by physical and chemical treatment, especially on the surface of a material. © 1998 John Wiley & Sons Ltd.