Controlling oxygen levels and using Variable Speed Drives (VSDs) on the combustion air fans on the reheating furnace helps to optimize combustion in the furnace. Excess air can substantially decrease combustion efficiency as it leads to excessive waste gases. Fuel-air ratios of the burners should therefore be checked regularly. The use of VSDs on combustion air fans on the reheating furnace also helps to control the oxygen levels, specially as the load of the furnace may vary over time. The savings depend on the load factor of the furnace and the control strategies applied.

Another way to control the oxygen levels is to increase oxygen content of the combustion air. This can be done either by mixing in ambient air or by using 100% oxygen. The reduction in exhaust gases can lead to substantial fuel savings. The fuel savings have to be compared to the cost of oxygen to estimate economic benefits (Worrell et al., 2010. p. 103).