In performance based structural fire safety design using the parametric fire curve, Eurocode has adopted a partial coefficient applied only on the fuel load density for calibrating the code to the desired safety level. Probabilistic analyses are presented in this paper to investigate the impact on the reliability due to variation of opening factor, and thermal inertia as well as the ratio between variable and permanent static load. It is shown that the partial coefficient method in Eurocode, with fire exposure expressed via parametric fire curves gives adequate reliability levels with certain margins on the safe side compared to stochastic evaluation based on the same assumptions. This margin is particularly high for load combinations with dominating variable load.