People say "lel" to make "lol" more playful or whatever, but if you search what LEL means on Google, you will find out LEL actually means "Lower
Explosive Limit". The Lower
Explosive Limit (LEL) is the lowest
concentration of a gas or vapour that will burn in air. The Lower Explosive Limit (LEL) varies from gas to gas, but for most flammable gases it is less than 5% by volume.