What is the theoretical oxygen limit in percentage below which combustion will not occur?

The theoretical oxygen limit refers to the minimum concentration of oxygen required to sustain combustion. In general, combustion requires oxygen in the range of approximately 11-15% by volume in the air for effective burning of hydrocarbon fuels. When the oxygen concentration falls below this threshold, the combustion process is inhibited, leading to incomplete combustion or an inability to ignite the fuel at all.

A concentration of 11% oxygen is commonly recognized as the lower flammability limit for many hydrocarbon fuels. At this percentage, there is sufficient oxygen for combustion to initiate and continue, making it a critical threshold for understanding combustion safety and efficiency in various applications, particularly within environments involving underground storage tanks and the handling of combustible materials.

Understanding this threshold is crucial for site assessments and safety protocols pertaining to USTs, as oxygen levels below this limit could indicate a risk of creating hazardous atmospheres where combustion could be dangerously limited or ineffective.