A device for trough extraction of exhaust air generated on a cooking hob, comprising: an exhaust air inlet opening arranged in a central recess of a cooking hob; a spiral-shaped fan housing having a motor-driven radial fan arranged on a bottom wall of the fan housing, the impeller of the radial fan carrying a plurality of uniformly spaced impeller blades, the fan housing having a fan suction opening spaced apart from the exhaust air suction opening, and the fan suction opening and the exhaust air suction opening having a common vertical center axis, the fan housing having an annular space arranged adjacent to the impeller blades, and the annular space being defined by the bottom wall, a top wall and an outer wall of the fan housing, the fan housing further having an exhaust air outlet opening provided by a free end portion of the bottom, top and outer walls (16, 28, 30) of the fan housing and by a side wall opposite the outer wall; a grease separation cartridge releasably connected with the exhaust air inlet opening and the fan suction opening, the grease separation cartridge forming an exhaust air conveying duct arranged vertically to a plane (E O) of the exhaust air inlet opening, the exhaust air conveying duct having a vertical center axis (M A) coaxial to the vertical center axis of the exhaust air inlet opening and the fan suction opening, wherein first and second grease separation means (40, 42) are arranged in the exhaust air conveying duct; and a two-part guide system having first and second guide units (46, 48) configured to radially distribute the exhaust air evenly and symmetrical in radial direction over 360° onto the impeller blades, characterized in that the first and second guide units (46, 48) have a common vertical center axis (M L) coaxial with the center axis (M A) of the exhaust air conveying duct, wherein the second guide unit is fixedly connected to an underside of the top wall of the fan housing and has a circular bottom arranged above the impeller onto which and adjacent to the impeller blades a flow grid ring is arranged, which flow grid ring has a plurality of uniformly spaced second flow lamellas which are radially aligned with respect to the vertical center axis (M L), and wherein the first guide unit is fixedly connected to a circumferential lower edge of the grease separation cartridge and has a bottom structure which is arranged within the flow grid ring on the bottom of the second guide unit and has a plurality of uniformly spaced first flow lamellas which are radially aligned with respect to the vertical center axis (M L) and communicate with the second flow lamellas. an exhaust air inlet opening arranged in a central recess of a cooking hob; a spiral-shaped fan housing having a motor-driven radial fan arranged on a bottom wall of the fan housing, the impeller of the radial fan carrying a plurality of uniformly spaced impeller blades, the fan housing having a fan suction opening spaced apart from the exhaust air suction opening, and the fan suction opening and the exhaust air suction opening having a common vertical center axis, the fan housing having an annular space arranged adjacent to the impeller blades, and the annular space being defined by the bottom wall, a top wall and an outer wall of the fan housing, the fan housing further having an exhaust air outlet opening provided by a free end portion of the bottom, top and outer walls (16, 28, 30) of the fan housing and by a side wall opposite the outer wall; a grease separation cartridge releasably connected with the exhaust air inlet opening and the fan suction opening, the grease separation cartridge forming an exhaust air conveying duct arranged vertically to a plane (E O) of the exhaust air inlet opening, the exhaust air conveying duct having a vertical center axis (M A) coaxial to the vertical center axis of the exhaust air inlet opening and the fan suction opening, wherein first and second grease separation means (40, 42) are arranged in the exhaust air conveying duct; and a two-part guide system having first and second guide units (46, 48) configured to radially distribute the exhaust air evenly and symmetrical in radial direction over 360° onto the impeller blades, characterized in that the first and second guide units (46, 48) have a common vertical center axis (M L) coaxial with the center axis (M A) of the exhaust air conveying duct, wherein the second guide unit is fixedly connected to an underside of the top wall of the fan housing and has a circular bottom arranged above the impeller onto which and adjacent to the impeller blades a flow grid ring is arranged, which flow grid ring has a plurality of uniformly spaced second flow lamellas which are radially aligned with respect to the vertical center axis (M L), and wherein the first guide unit is fixedly connected to a circumferential lower edge of the grease separation cartridge and has a bottom structure which is arranged within the flow grid ring on the bottom of the second guide unit and has a plurality of uniformly spaced first flow lamellas which are radially aligned with respect to the vertical center axis (M L) and communicate with the second flow lamellas.