Currently, most lighting manufacturers operating in the European market provide the life for their LED luminaires in the format: time LxBy, such as 50000h L80B10. Thus, the described life gives information in terms of the expiration of LED luminaires during their use. However, it does not refer to their damage. The individual components of the life notation should be understood as follows:
Time [hr] - the time after which the parameters described by the coefficients Lx and By are expected to be achieved.
Lx - luminous flux maintenance factor, determining the percentage limit x of the decrease in the luminous flux emitted by the LED luminaire at the end of the declared time.
By - a population factor specifying the expected percentage y of the population of, for example, used LED luminaires whose emitted luminous flux level does not meet the Lx criterion at the declared time.
The example notation 50000h L80B10 should be understood as the time during which the luminous flux emitted by 10% of the population of used LED luminaires will fall below the declared 80% threshold of its initial value
The most common is the so-called average useful life, where the time and luminous flux maintenance factor (Lx) are declared for the population index B50. In the case of a luminaire using multiple LED chips or modules, the notation 50000h L70B50 means that in the declared time the luminous flux emitted from the LED luminaire should not be lower than 70% of its initial value.