# Upper Explosive Limit (UEL) #fundamental #gas-detection #safety The Upper Explosive Limit (UEL) is the maximum concentration of a flammable gas or vapor in air that can ignite. Above the UEL, the mixture is too rich to burn. ## Key Points - The range between LEL and UEL defines the flammable range - Methane has a UEL of approximately 15% by volume - Above the UEL, there is insufficient oxygen for combustion - The flammable range varies significantly between different gases ## Flammable Range The area between LEL and UEL is where the gas-air mixture can ignite: - Below LEL: Too lean to burn - Between LEL and UEL: Flammable range (dangerous) - Above UEL: Too rich to burn ## Safety Implications Understanding both LEL and UEL is essential for: - Proper gas detection system design - Setting appropriate alarm thresholds - Understanding explosion risks in different scenarios ## Related Concepts - [[Lower Explosive Limit - LEL]]