LOWER EXPLOSION LIMIT
[EN 14034-3; ASTM E 1515]
The lower explosion limit (LEL) is the concentration of the combustible material, above which the mixture with air can be ignited to result in an explosion.
The LEL is determined with an ignition energy of E = 10.000 J in a 20-ℓ-Apparatus.
The concentration of the combustible material is varied, until the concentration limit is found, below which no ignition occurs in three trials with the optimum delay time.
For explosion protection concepts, which are based on the elimination or avoidance of explosive atmospheres, the LEL must be precisely known to make evident, that under process conditions and deviations, no explosive mixture is formed.