Combustion within any type of air-breathing jet engine is quite inefficient. Of all the oxygen entering the front of the engine, no more than about a quarter is actually used to burn fuel within the engine. To make the process more efficient, then, some jet engines are also equipped with an afterburner. The afterburner is located directly behind the turbine in the jet engine. It consists of tubes out of which fuel is sprayed into the hot exhaust gases exiting the tubing. Combustion takes place in the afterburner, as it does in the combustion chamber, providing the engine with additional thrust. In a typical jet engine of moderate size, an afterburner can increase the takeoff thrust from about 50,000 N (11,000 lb) to about 70,000 N (15,500 lb).