[en] Eurocode 5, Part 1-2, presents several models for the calculation of fire resistance of timber structures. These models are based on the hypothesis that for temperatures above 300°C, wood is no longer able to sustain any stress, which makes the determination of the location of the 300°C isotherm decisive for the result provided by the models. In this paper, the charring rate model and the conductive model presented in Eurocode 5, part 1-2 are compared regarding the determination of the location of 300°C isotherm. The main wood parameters investigated are density, moisture content and anisotropy. the almost complete independence of the charring rate model from these parameters leads to some inconsistencies between the models. To reduce thse inconsistencies some proposals to improve the conductive and the charring rate models are presented.