The chemical reduction of pure molybdenum trioxide or ammonium dimolybdate to metal requires two stages because conversion directly to metal releases heat that inhibits the process. The first stage reduction to MoO2 is performed in the 450-650°C range. Molybdenum dioxide is then reduced to molybdenum metal in second stage reduction, using temperatures in the 1,000-1,100°C range. Historically, both stages were accomplished by pushing boats loaded with powder through tube furnaces containing a flowing hydrogen atmosphere. Rotary furnaces, where powder is fed continuously through a rotating inclined tube in a flowing hydrogen atmosphere, are becoming common in first stage reduction operations, where they provide increased production efficiencies.