This is sub-report 2 of the BRAVENT project (Fire and smoke distribution in ventilation ducts) which presents results from experiments where the risk of spreading fire and heat in ventilation ducts has been investigated. In the experiments, the effect of fire insulation on the duct, and mixing hot smoke with air at room temperature in the duct (as from adjacent rooms) has been investigated. The ventilation duct was connected to a furnace at one end and a fan at the other end. The furnace was heated to the desired temperature, and hot smoke was drawn through the duct at a certain velocity. Thermocouples measured the temperature both inside the duct (smoke gas temperatures) and on the duct’s external surface at different distances from the furnace.