A ventilation system, the ventilation system comprising a main duct connected to at least one motorized fan, and further connected to at least one workplace (Wa; Wb; Wc) via a local duct arrangement (102a; 102b; 102c), a gate arranged in a position between the workplace (Wa; Wb; Wc) and the main duct and a control computer, wherein said local duct arrangement (102a; 102b; 102c) comprises an asymmetrical bend duct section having a straight duct portion connected to a bend duct portion, said asymmetrical bend duct section being defined by a circumferential wall portion forming as seen along the longitudinal extension of the asymmetrical bend duct section a first duct opening facing the workplace (Wa; Wb; Wc) and a second duct opening facing the main duct, said ventilation system further comprising a first pressure sensor arranged on the outside of the asymmetrical bend duct section and in fluid communication with the interior of the asymmetrical bend duct section via a first through-going opening arranged at a first position in the circumferential wall portion of the straight duct portion, and a second pressure sensor arranged on the outside of the asymmetrical bend duct section and in fluid communication with the interior of the asymmetrical bend duct section via a second through-going opening (123; 123') arranged at a second position in the circumferential wall portion of the bend duct portion or in a duct section connected to the bend duct portion, wherein said first and second positions are arranged along an inner curvature of the asymmetrical bend duct section, wherein said first and second pressure sensors (120; 122) are configured to communicate with the control computer, wherein said control computer is configured to determine, based on input signals from the first and second pressure sensors (120; 122), a pressure difference between the positions of the through-going openings (121; 123; 123') of the first and second pressure sensors (120; 122), and wherein said control computer is further configured to control the speed of the motorized fan based on the determined pressure difference. wherein said local duct arrangement (102a; 102b; 102c) comprises an asymmetrical bend duct section having a straight duct portion connected to a bend duct portion, said asymmetrical bend duct section being defined by a circumferential wall portion forming as seen along the longitudinal extension of the asymmetrical bend duct section a first duct opening facing the workplace (Wa; Wb; Wc) and a second duct opening facing the main duct, said ventilation system further comprising a first pressure sensor arranged on the outside of the asymmetrical bend duct section and in fluid communication with the interior of the asymmetrical bend duct section via a first through-going opening arranged at a first position in the circumferential wall portion of the straight duct portion, and a second pressure sensor arranged on the outside of the asymmetrical bend duct section and in fluid communication with the interior of the asymmetrical bend duct section via a second through-going opening (123; 123') arranged at a second position in the circumferential wall portion of the bend duct portion or in a duct section connected to the bend duct portion, wherein said first and second positions are arranged along an inner curvature of the asymmetrical bend duct section, wherein said first and second pressure sensors (120; 122) are configured to communicate with the control computer, wherein said control computer is configured to determine, based on input signals from the first and second pressure sensors (120; 122), a pressure difference between the positions of the through-going openings (121; 123; 123') of the first and second pressure sensors (120; 122), and wherein said control computer is further configured to control the speed of the motorized fan based on the determined pressure difference.