Fuel-burning engines generally produce nitrogen oxides (NOx) that can react with the ozone in the atmosphere.

Supersonic aircraft engines operate partly in the stratosphere at the level of the ozone layer. It is therefore essential to reduce emission of these gases.

Lean premixing combustion chambers reduce NOx emissions by at least 80 percent. They will equip future supersonic aircraft. These combustion chambers, where the jet fuel is mixed with air then vaporised in the premixing duct, risk being destroyed by auto-ignition . This phenomenon is studied on a test facility where alerts are detected by optical fibres connected to photocells .