Over time, the gradual reduction in the quality of light emitted from any High
Intensity Discharge lighting system occurs for a number of reasons, called
light loss factors. In contrast to HID light sources, Low Pressure Sodium systems generally maintain constant lumen output over life. Light Loss
Factors that do affect Low Pressure Sodium lamps are luminaire dirt depreciation,
deterioration of luminaire surfaces, dirt on room surfaces and supply voltage.
Ambient temperature generally has no effect on the light output of Low Pressure
Sodium lamps.
