NOVELTY - Device (100) comprises (a) a feed device (30), (b) a tubular furnace (20) having an inlet zone, an interior space, a rotational axis and an outlet side, (c) a water supply (31) arranged in the region of the feed device or inlet zone to add water to the starting material, (d) a gas guiding system (40) arranged on the outlet side of the tubular furnace, for forwarding the gas mixture, and (e) a gas monitor arranged in the region of the gas guiding system, for monitoring the proportion of hydrogen in the gas mixture.    USE - The device is useful for reacting an organic starting material, preferably carbonaceous or hydrocarbon-containing starting material to a hydrogen-containing gas (all claimed).    ADVANTAGE - The device makes use of waste materials, residual materials and biomass and so is environmentally friendly, and has improved stability at high temperatures.    DETAILED DESCRIPTION - Device (100) comprises (a) a feed device (30), (b) a tubular furnace (20) having an inlet zone, an interior space, a rotational axis and an outlet side, (c) a water supply (31) arranged in the region of the feed device or inlet zone to add water to the starting material, (d) a gas guiding system (40) arranged on the outlet side of the tubular furnace, for forwarding the gas mixture, and (e) a gas monitor arranged in the region of the gas guiding system, for monitoring the proportion of hydrogen in the gas mixture. The feed device and the tubular furnace are arranged and formed such that the starting material in region of the inlet zone is supplied into the interior space of the tubular furnace through the feed device, and a solid material and a gas mixture are delivered to the outlet side of the tubular furnace. The tubular furnace comprises a first zone located in a region between the inlet zone and the second zone, a second zone located in a region between the first zone and the outlet side, and a compensator for compensating different thermal induced expansions of the first zone and the second zone. The water supply is controlled depending on the proportion of hydrogen in the gas mixture.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the device.    Tubular furnace (20)    Feed device (30)    Water supply (31)    Gas guiding system (40)    Device (100)