Various discharge cleaning techniques have been studied in Microtor. It was found that high temperature discharges are not only ineffective in reducing the oxygen on the wall, and hence in the plasma, but may even induce trapping. Oxygen can be removed from the wall by a low-temperature, partially ionized hydrogen plasma by conversion to water vapour. The amount of loosely bound oxygen on the surface is thus reduced below 1% of a monolayer. The residual amount of the oxygen in the plasma is near 1010 atom · cm−3, and represents a significant improvement over previous tokamak results.