The reducing atmosphere, rich in CO and H, can be created from the high-temperature cracking of natural gas at around 1100-1150 °C, in the presence of oxidized gases (HO and CO) from ore reduction reactors.
          + CO → 2 CO + H</small>
 + HO → CO + 3 H</small>
The system that generates the reducing gases is called a "reformer". In the Midrex process, it consists of tubes heated by the combustion of a portion (around a third) of the gas from the reactor.