What is the upper flammable limit (UFL) of methane in air?

The upper flammable limit (UFL) of methane in air is approximately 15%. This means that when the concentration of methane in the air exceeds this percentage, the mixture becomes too rich to ignite. Combustion requires an appropriate balance of fuel and air; at the UFL, there is not enough oxygen available in the mixture for ignition, which is why concentrations above this limit do not support combustion.

For methane, the flammable limits are typically understood in terms of both the lower flammable limit (LFL) and the UFL. The LFL is around 5%, indicating the minimum concentration of methane needed for combustion to occur. Understanding these limits is crucial for safety in environments where methane is present, such as industrial sites and natural gas facilities. Proper safety measures must account for the possibility of methane concentrations reaching these critical thresholds.