If the steel heats up during a fire, the structure will gradually lose its load-bearing capacity between 350ºC and 750ºC. Depending on the empty load of the structure, it will usually go up when the steel reaches a temperature of 500-600 ºC. Therefore, protection of steel structures in case of fire is necessary to maintain the structural stability of the building. The required thickness of each product depends on: the fire resistance requirement (usually R30, R60, R90 or R120 minutes, sometimes even R180 or R240 minutes, according to local laws and mostly depending on the function and height and the activities inside the building) and the design critical temperature.
There are several ways of covering steel with fireproofing, be it with fireproof paint, fireproof stone wool, fireproof tiles or fireproof plasters.