What is the minimum oxygen percentage required to sustain combustion?

To sustain combustion, a minimum oxygen concentration of around 15% is necessary. In the atmosphere, oxygen makes up about 21%, which is typically sufficient for most combustion processes. When oxygen levels drop below this threshold, the combustion reaction becomes less efficient, and flames may extinguish.

Engines, furnaces, and similar systems are designed to operate optimally in air that consists of approximately 21% oxygen. If the oxygen concentration falls below 15%, the ability to maintain combustion is significantly impaired, leading to incomplete burning or extinguishment of the flame. This understanding is critical in fire safety, firefighting strategies, and various industrial applications where controlled combustion is essential.