The materials used in buildings are collectively referred to as building materials. The burning properties of building materials refer to all physical and chemical changes that occur during combustion or fire. This property is caused by the ignitability and flame spread of the surface of the material, heat generation, fuming, charring, weight loss, and toxic products. Produce and other characteristics to measure. China's national standard GB8624-97 divides the combustion performance of building materials into the following grades. Class A: Non-combustible building materials: Materials that hardly burn. Grade B1: Flame retardant building materials: Flame retardant materials have good flame retardant effects. When it encounters an open flame in the air or it is difficult to catch fire under the action of high temperature, it is not easy to spread quickly, and the combustion stops immediately after the fire source is removed. Class B2: Combustible building materials: Combustible materials have a certain flame retardant effect. In the air, when exposed to fire or under high temperature, it will immediately ignite and burn, which may lead to the spread of fire, such as wooden columns, wooden trusses, wooden beams, wooden stairs, etc. Grade B3: Flammable building materials: no flame retardant effect, extremely flammable, and dangerous to fire.