The most important condition that must be fulfilled by designing and performing any construction is safety in the way that the construction is able to withstand all predictable, persistent and accidental actions. Fire refers to accidental action and probability of its appearance is low, which is why fire was not given much attention to the design and implementation of safety measures until recently. However, if a fire occurs, its consequences are great material damage, and sometimes human sacrifices. In this paper, the concept of fire protection will be elaborated and the main focus will be on steel structures that are very sensitive to the effects of high temperature caused by fire. The papper is divided into a theoretical and practical part. The theoretical part briefly describes the laws and regulations in the field of fire engineering in Croatia, explaining the formation and behavior of fire in indoor areas as well as measures for fire protection. The concept of calculation of steel structures, which includes the properties of steel at normal and elevated temperatures, the determination of temperature in steel elements and the calculation of the Eurocodes, is also presented. Practical part of the papper shows the flow of calculation of the resistance of the construction exposed to the fire. The aim was to achieve fire resistance R30 so it was necessary to carry out certain protection measures because the unprotected construction does not meet the required resistance. With SCIA Engineer 17.01, calculations for three protection measures were carried out, and the results were compared in the end.