The fire behaviour of polyether polyurethane foam has been studied at three scales: matter scale, small scale and product scale. A method to determine the thermal decomposition mechanism of materials was defined at the matter scale. This method is based on the analysis of the mass-loss rate (solid phase) and gas release (gas phase) obtained in thermogravimetric analysis coupled to FTIR gas analysis. Using a model and genetic algorithms, the kinetic parameters of the decomposition process were calculated, which allowed an accurate prediction of the mass-loss rate. Measurements of heat release rate and gas release were carried out in cone calorimeter coupled to gas analysers (small scale). This data as well as the results from the model were used as input data for the numerical simulation of fire behaviour. This study highlighted that some improvements need to be carried out to the simulation codes. Measurements of heat release rate and mass-loss rate were also performed during the fire of a simplified piece of upholstered furniture (product scale). It was pointed out that the decomposition mechanism of the foam remains unchanged independently of the scale analysed.