By monitoring the furnace exhaust gas flow rate and composition, the use of chemical energy in the furnace can be enhanced. With the aid of optical sensors, post-combustion of off-gases can be investigated in detail and the findings can be used to optimize off-gas post-combustion operations.  Benefits of this practice include reduced electricity consumption, shorter power-on times, increased productivity, a decrease in production costs, a reduction of electrode consumption, reduced natural gas, oxygen and carbon consumption, and a reduction of refractory wear. For example, significant improvements in the off-gas chemical energy recovery have been realised by continuously adjusting the oxygen injection for post-combustion based on real time readings of CO and CO₂ concentrations in flue gases (Worrell, et al., 2010. p. 90).