The object of research is a single-span metal frame. Since the fire resistance of metal-bearing structures is insignificant, this is because at temperatures above 400 °C for steels and more than 200 °C for aluminium alloys, significant development of plastic deformations under constant load (creep) begins to manifest itself. The purpose of this work is to conduct research aimed at studying various emergency impacts, in particular, the impacts associated with heating during a fire and its effect on the stability of both individual elements and the entire structural system. To meet the new requirements of Federal Law "Technical Regulations on the safety of buildings and structures". To identify the influence of the heating temperature of the gas medium on the mechanical characteristics of steel structures by obtaining data from the accepted regularity and constructing a trend line and by the method of displacements, taking into account kinematic definiteness, to investigate the effect of temperature at uniform heating during a fire on the value of critical parameters of a single-span frame. By solving some problems that arose during the study, we can say about the necessity to improve steel structures to prevent irreversible consequences during an emergency. The research's main results are to identify the relationship between the temperature of the medium on the mechanical characteristics of steel structures.