What deficiency of oxygen in a methane-air mixture makes an explosion impossible?

In the context of methane-air mixtures, an explosion cannot occur if the oxygen concentration falls below a specific threshold. The correct answer, indicating that an oxygen deficiency of 12% renders an explosion impossible, is based on the principles of combustion and the flammability limits of methane.

For methane to ignite and potentially cause an explosion, there must be a sufficient concentration of both methane and oxygen within a specific range. The lower flammability limit (LFL) for methane in air is approximately 5% by volume, which means there must be at least 5% methane present. However, alongside that, there must also be an adequate level of oxygen.

At 12% oxygen concentration, the mixture lacks enough oxygen to support a viable combustion reaction, regardless of the amount of methane. This threshold is crucial, as below this level, the mixture will be too lean to sustain combustion. Therefore, while a higher concentration of oxygen (like 15% or even 9%) can support combustion if the methane concentration is suitable, a reduction to 12% oxygen effectively prevents a potential explosion scenario.

Thus, the significance of understanding these percentages lies in the safety regulations and guidelines in mining operations, ensuring that conditions are maintained to prevent explosive atmospheres