A zero oxygen balance occurs when the amount of oxygen in an explosive is exactly enough to fully react with the fuels in the mixture. Having a zero oxygen balance makes the blast efficient (i.e., rock is well fragmented), cost effective, and limits the amount of harmful gases produced.

A positive oxygen balance has too much oxygen and can produce noxious gases termed NO_x (i.e., by the extra oxygen reacting with nitrogen in the air); a negative oxygen balance creates carbon monoxide (i.e., the combustion of the organic carbon in the fuel is not complete, so CO forms instead of CO₂).