Thus Structures have an increed Fire Resistance Limit. The Shape of Such Doors Calmly Tolerates High Temperatures and Does Not Deform. Fire Metal Doors Will Never Jam. Toor IS SLIGHTLY Inflated During A Fire. But in this case, you can still get out of the premises. Insulate Such Doors with A Special Material, Which Prevents Their Heating and Jamming. It can be minerel wool fiber or asbestos. All these Materials are Durable, Simple and Reliable. When The Temperature Rates, This Material Expands and Foam. In the room, smoke is blocked. The Door Itself Does Not Heat Up.