Our client designed an extraction hood for a steel mill with a flow rate of 430 kg/s Flow Control Engineering was hired to validate it and ensure that it would not have any problems in its operation The calculations showed that there would be cross flow caused by the overall design of the ducts Due to the three dimensional design, the flow was rotating in relation to its interior and therefore the air upstream, under the hood as well We designed appliances to avoid this behavior The pressure drop was reduced by 15 and cross flows were prevented The plant was successfully put into operation while maintaining a high clean environment for the operators and the surroundings.