n. The ratio of the mass of a substance produced by combustion per unit mass of fuel consumed.
Combustion of woody fuel or other hydrocarbons produces a variety of gases (such as carbon monoxide, carbon dioxide, methane, and water) and particulates. Emission factors relate the mass of a given species generated by the combustion of a unit mass of fuel. These factors depend, in part, on the type of fuel, the atmospheric conditions of combustion, the rate of combustion, and the combustion stage (such as pyrolysis, flaming combustion, or smoldering combustion). For particulate matter, higher emission factors indicate less efficient combustion.