What are the differences between first-level fire-resistant materials and second-level fire-resistant materials?
1, these refer to fire resistance rating of building materials. 2, As for steel, elements that used in different parts should reach different duration of fire resistance according to fire resistance rating. For example, fire resistant pillars of first level can endure fire within 3 hours; the second level, 2.5 hours; the third level, 2 hours. With respect to beams, three levels of fire resistance are included.
Level B1: building materials with flame retardancy: this kinds of materials have good effect in flame retardation. Under the case of open fire or high temperature, it is not easy to be ignited and spread quickly, and when the fire source is removed, fire would stop immediately. Level B2: combustible building materials: combustible building materials also have effect in flame retardation. It will get burnt as soon as it meets open fire or high temperature, so it can easily give rise to rampant fire, such as wooden pillars, wood roof trusses and wooden stairs.
The combustion performance of materials could be divided into: A( noninflammability), B1(flame retardancy), B2(flammability), B3(inflammability). Building materials are divided into four ranks according to these properties. 1. In accordance with Code for Design of Building Fire Protection(GBJ16-1987)(revised edition in 2001), fire hazards in producing and storage can be divided into five types. In Fire Prevention Code of Petrol Chemical Enterprise Design(GB50160--1992)(revised edition in 1999), classification of fire hazards is also achieved according to the hazards of materials that have been using, producing and storing. Measures in prevention of fire explosion could be taken from the perspectives of fire separation, fire resistance level of structures, allowable floors, safe evacuation, and fire extinguishing facilities based on different levels of fire hazards. 2. Four fire resistance rating of buildings are listed in the book Code for Design of Building Fire Protection. And specific stipulations are made to the fire resistance of main elements of buildings, such as bearing walls, beams,pillars, and floors. When designing a building, if permitted, refractory materials of high-rank should be adopted in those buildings which have high potential fire hazard and a lot of combustible material and valuable equipment. While making sure fire resistance rating, the duration of fire resistance of each elements should meet its requirements.
