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. <EOS>