Define the Upper Explosive Limit (UEL).

The Upper Explosive Limit (UEL) is defined as the highest concentration of a flammable gas in air that can sustain combustion. Above this concentration, there is too much fuel present for the air to support a flame, meaning the mixture cannot ignite. This is critical for understanding explosion hazards, as it helps safety professionals determine the safe handling and storage practices for flammable materials.

In contrast, the lowest concentration of a flammable gas in air is known as the Lower Explosive Limit (LEL), while the exact concentration of gas needed for combustion is more of a theoretical measurement than a fixed point. The ideal fuel-to-oxidizer ratio is relevant to combustion efficiency but does not directly define the upper limits for explosive potential. Understanding the UEL allows individuals to recognize safe operating conditions and prevent hazardous situations in environments where flammable gases might be present.