Combustion efficiency refers to the amount of products of incomplete combustion released relative to the amount produced from theoretically perfect combustion, expressed as a dimensionless percentage. Because perfect combustion produces only CO2 and water, its combustion efficiency is 1.0. In combustion of widland fuels, combustion efficiency can roughly range from as high as 0.95 for flaming combustion to 0.65 for smoldering combustion.
Source: Hardy, Colin C., Ottmar, Roger D., Peterson, Janice L., Core, John E., and Seamon, Paula. 2001. Smoke Management Guide for Prescribed and Wildland Fire 2001 Edition. Produced by the National Wildfire coordinating Group Fire Use Working Team.