In today's world, light-emitting diodes are quickly replacing conventional light sources, both indoors and outdoors. Being a solid-state device, adverse ambient conditions such as high temperature and humidity lead to its poor performances, light quality and longevity. In outdoor applications, exposure to high ambient temperature during daytime, even when the lamp power is off, causes the lamp performance to deteriorate. In tropical countries, the environmental temperature in most of the days is higher than 25℃ and sometimes reaches 50℃. Here, the humidity varies between 30% and 80% and frequently over 80%. Thus, the reliability of the light emitting diodes is a question that needs a thorough study. In line with this, in this study, an effort has been made through an experiment. Here, commercially available surface-mounted device and chip-on-board-based light-emitting diodes are tested through an environmental chamber, and their measured illuminance values were observed by varying the relative humidity. Then, the temperature ageing or stress was set at 60℃ on the above types of light-emitting diodes at power off condition for 6000 hours and after that its luminous flux and spectral distribution were observed. The degradation observed under these conditions may guide designers and manufacturers to upgrade their lighting systems to make them fit for tropical conditions.
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