The thesis aims at studying three fire door assessment paramenters, given as door backside surface temperature, irradiance and distortions at specified locations for one-plate and dual-plate steel fire door with specified structural framework and different heating surface respectively. The test program adopted CND 11227 A3223 testing method as the one for conducting test. From the results obtained, the performance parameters of fire door on both sides and different structural arrangements being tested showed little differences. In contrast, among those parameters of dual-plate door test distortion values show a relativiely strong dependency on structural framework arrangement and chosen side to be heated. It was shown that irradiance and backside surface temperature of dual-plaste door experiment were larger than one-plate door's case.