What Does
Upper Explosive Limits Mean?
Upper explosive limits (UEL) are the maximum concentrations of a gas or vapor in the atmosphere that is able to generate a flash or a fire in the presence of an ignition source. A gas or vapor that has a higher concentration than the upper explosive limit will not be able to burn as it will be too rich.
Safeopedia Explains Upper Explosive Limits
The opposite of the upper exposure limit is the lower explosive limit. This is the lowest concentration in the atmosphere of a gas or vapor that is required to generate a flash or a fire. The range between the lower and upper exposure limits is known as the explosive range. In the explosive range, a gas or vapor will readily ignite.