Any modern doors have some fire resistance due to non-flammable materials that are used in their manufacture. But at the same time, it should be noted that such stability has a short period of time. The design of fire doors is such that they are not affected by fire much longer. The top protective layer of ordinary fire doors has steel sheet, or aluminum, or wood or other. Specialists have specially developed this technology, conducting a lot of tests.
From the inside, the door is filled with heat-insulating material and an anti-smoke gasket that blocks the way into the building of toxic substances that are released during combustion. The most fire-resistant doors have a steel outer layer and an inner layer made of stone wool (mineral fire-resistant wool). The groove of the entire perimeter of the door has a special strip that resembles hard clay or plasticine. This insert begins to foam during a fire and at the same time begins to seal the cracks. Therefore, the room is isolated from the toxic combustion product. It is worth noting that if you plan to use an English-style interior, then such a door design will be a good addition.
In order to minimize the heating of the door surface on the side that the fire does not touch, heat insulators (heat-insulating gaskets) are added to the metal door structure. A heat insulator is, for example, a mineral plate, which includes basalt fiber in its base. The period of decay of the plate depends on the size of the fiber from exposure to high temperature. Silica is the most successful heat-insulating material, it can easily withstand temperatures up to 1200C and for a short period up to 1800C. If you want, the door structure can be additionally coated with a special composition, which will increase its service life.
You can buy a similar design only in a specialized store. But in order to get acquainted with the main models, you can use information from specialized sites. It is also noted here what aspects should be taken into account in order to choose a really high-quality product. Thus, you can choose a really high-quality door structure.