What happens to oxygen availability when Methane levels exceed 15%?

When methane levels exceed 15%, it creates a condition known as an explosive or flammable environment, which impacts the availability of oxygen. In such scenarios, the combustion of methane consumes oxygen from the atmosphere, reducing the overall oxygen availability. This is significant because in environments with high concentrations of combustible gases like methane, there can be a risk of displacement of oxygen as it is used up in the combustion process. Therefore, as methane concentrations rise, they can lead to diminished oxygen levels, which creates a hazardous situation for both breathing and potential combustion risks.

The remaining choices do not accurately capture the relationship between methane levels and oxygen. For instance, the idea that oxygen is abundant contradicts the reality that increased methane usage leads to oxygen depletion. Similarly, fluctuations in oxygen levels do not account for the consistent reduction expected in an environment with high methane concentrations, and increased levels of inert gases are not a direct result of elevated methane levels themselves, as these gases do not consume oxygen in the same active way.