What classes are divided by fire doors
Steel doors are divided into several types. This is done primarily by the degree of security from hacking. In this regard, the doors are divided into 4 classes. The most protected doors of the 4th class are considered that can protect the door from any type of small arms. In addition, the doors are divided by the degree of fire resistance and impermeability of the air, as well as the degree of sound insulation.
The standard steel door of the so-called “economy class” has a design consisting of a door box, which is attached to the wall with special crossbars penetrating the wall to a depth of 15 cm and the door leaf itself with a complex section. In addition, the door has three loops with bearings and a system of protection against cutting loops. High -quality doors necessarily have a layer of insulation and polyurethane aggregate.