What happens when a flammable gas reaches its flammable limit?

When a flammable gas reaches its flammable limit, it becomes capable of igniting with a spark or flame. The flammable limit refers to the specific concentration range of a gas in air that can support combustion. Below the lower flammable limit, there is not enough gas to sustain combustion; above the upper flammable limit, there is too much gas, and the mixture is too rich to ignite. Therefore, when the concentration of the gas is within this defined range, any introduction of an ignition source, such as a spark or flame, can result in combustion. This understanding is critical for ensuring safety during the handling and storage of flammable gases, as it emphasizes the importance of maintaining concentrations outside of these limits to prevent accidental ignition.