What are the lower and upper explosive limits (LEL and UEL) of methane gas?

The lower and upper explosive limits (LEL and UEL) of methane gas are indeed 5% and 15%. These limits refer to the concentration of methane in the air, below which the gas will not ignite (LEL) and above which will not sustain combustion (UEL).

Methane’s LEL being at 5% means that at concentrations lower than this level, there is not enough methane mixed with air to form an ignitable mixture. Conversely, the UEL at 15% indicates the point beyond which there is too much methane in the air for combustion to occur. Understanding these limits is critical for safety in environments where methane may be present, like in certain engine fuel systems, to avoid accidental ignition and explosions.

This knowledge is vital not only for ensuring safe handling and use of methane but also for effective monitoring and preventative measures in any operation involving gas fuel systems.