What is the maximum amount of gaseous fuel present in an air mixture for it to be flammable called?

The maximum amount of gaseous fuel present in an air mixture for it to be flammable is called the upper explosive limit (UEL). This term defines the concentration of gas in the air above which the mixture is too rich to ignite. To effectively combust, a fuel-air mixture must fall within a specific range known as the flammable range, which is bounded by the lower explosive limit (LEL) and the upper explosive limit (UEL).

The UEL indicates the point at which additional fuel does not enhance combustion because the mixture lacks sufficient oxygen to sustain a fire or explosion, making it a critical concept in fire safety and hazard analysis. Understanding these limits helps fire inspectors ensure safe handling and storage of flammable materials.