The term FIRE implies uncontrolled burning which endangers material values and human lives. It has long been considered that the use of steel as load-bearing structures is much more unfavorable than reinforced concrete structures.
Modern methods can achieve high requirements in terms of fire resistance of steel structures. The choice of fire safety system depends on the probability of fire.
The required fire resistance for steel structures is presented in units of time - 15,20,45, 60, 90 and 120 '. The fire resistance of a steel element depends on its cross-sectional factor.
Elements with a lower cross-sectional factor heat up more slowly, which requires less insulation to achieve the same fire resistance, and vice versa. Steel elements with a high cross-sectional factor heat up much faster, so the insulation thickness (expressed in microns) increases in proportion to the cross-sectional factor.