This thesis addresses the behaviour of glass in fire condition. The behaviour of glazing could influence the growth of fires. Radiation is often the most significant heat transfer mechanism and its modelling is critical to an accurate prediction of temperature distribution in the glass and the time to breakage. A literature review on the theoretical modelling and experimental aspects of glazing systems exposed to fire are presented. Theoretical issues of glazing modelling in fire conditions were identified. To address the limitations of existing approaches, a more robust computer tool, referred to as Fire Dynamics Simulator - One Dimensional & Three Dimensional Spectral Discrete Ordinate Method (FDS-1D & 3D-SDOM) was developed in this thesis. The new computer tool is comprised of (i) a CFD part for the fire dynamics and fluid flow simulation, (ii) a spectral Discrete Ordinates radiation model for radiative source term calculations in the glass, and (iii) a FEA part for the 3D thermal conduction thermal stress, thermal strain and the probability of failure in glass material. For verification purposes, the model is applied to some typical fires/glazing scenarios from the literature. Good agreements are found between predictions and experimental data. The study also investigates the effects of the glass thickness, thermal conductivity and emissivity on the glass temperature.