A gas generator comprising a substantially cylindrical gasifier vessel (1), a grate (2) on which solid fuel (8) being combusted is fed, a gasifier throat (6) forming in the gasifier vessel (1) a portion with a cross section narrower than that of the other portion of the gasifier, and gasification air nozzles (4) adapted above the gasifier throat (6) to the gasifier vessel (1). The invention is implemented by way of adapting at the gasifier throat (6), substantially concentric with the center axis of the cylindrical gasifier vessel (1), an upward tapering control element (5) of the gasifier throat cross-sectional area.