The investigation of fires spreading in ships' cabins by use of practically validated computer modelling is part of a major research programme and work is reported regularly [2 - 4]. The model here reported deals with the spread of fires in cabins under forced ventilation conditions. The essential problem is that of the movement and temperature histories of combustion products as buoyant, turbulent, circulating flows in a three dimensional enclosure. For the present work, the source fire was located on a cabin bed adjacent to the rear wall of the cabin. A three dimensional steady state field model was developed, comparable to a fire in the nearsteady operational plateau of its life. The related computational fluid dynamics (CFD) work being based on the FLUENT code. The above references give details of the CFD code, the experimental arrangements and the layout of the full-scale cabin used for the progressive validation. The present investigation included models of forced ventilation with differing extracting fan flow rates, equivalent to a fan speed range of 3 to 25 m/s. In general, with an extraction speed up to 10 m/s, there was a modest effect compared to natural ventilation with the fan enhancing the entrained air flow condition around the fire plume. The ensuing deflection of the fire plume towards the rear wall had an almost negligible effect in changing the plume behaviour. As the fan flow rate increased up to 25 m/s, there was clearer evidence of asymmetric flow due to the increase in air entrained towards the fire. The deflection of the fire plume towards the rear wall was increased significantly as a result of the net pressure difference between the entrained air and the fire plume. This behaviour increased the effect of the rear wall in enhancing the fire plume, the spread over the wall giving a larger area over which to entrain air to bum the residual fuel volatiles.