choinecheekly

Дата: Воскресенье, 08.09.2013, 18:24 | Сообщение # 1

Группа: Гости

Another type of door that cannot meet the test for fire rating under NFPA 252 is the honeycomb core (hollow-core) wood door, commonly used in residential and business occupancies http://sandsand.site90.net. This door is made up of two thin veneers of wood http://stroitel.net16.net separated by a honeycomb of thin wood or fiberboard strips.
Photo 2 shows the construction of a slab door with a particle-board core. This type of door is made of a slab of particle board (wood fibers and adhesive) with a wood veneer glued to both faces. This type of door can meet the test for fire ratings up to one hour according to NFPA 252 and is frequently used in fire-rated assemblies in residential and business occupancies.
Photo 3 shows the construction of a wooden slab door with a gypsum (kalamein) core. This type of door appears similar to a slab door with a particle-board core except that the core is gypsum material like that used in drywall board. http://stroitelstvo.comlu.com This type of door can meet the test for higher levels of fire rating under NFPA 252 than the particle-board core. This door type is frequently used in fire-rated assemblies in schools, patient-care facilities, and commercial buildings. It is also manufactured of steel instead of wood veneer and is filled with gypsum material.
Some older kalamein doors had a core of asbestos cement instead of gypsum. Although the asbestos core is no longer used because of the health hazard of asbestos, many of these doors are still present in structures built before 1980.