Abstract: A heating oven for use in ageing semiconductors comprises a heating chamber 5 for receiving a number of trays 10 of semiconductors. Each tray 10 can be passed into the heating chamber 5 and ejected from the heating chamber 5, without disturbing the temperature environment of the remaining trays 10 in the heating chamber 5. This is achieved by the provision of closeable openings 13 on the wall 11 of the heating chamber 5 through which trays 10 may be passed.