High Pressure Sodium (HPS) or High Intensity Discharge (HID) is a form of lighting that is widely used as indoor grow lights for hydroponic growers, domestic to commercial.
HPS lamps emit light when an electrical current is run through the arc tube that has been filled with gas. The gasses found within a HPS globe is a mixture of sodium and an inert gas Xenon. Xenon is used as a starting gas. Current and temperature increase in the tube until it reaches full output.
HPS lamps have a spectral range from 570nm up to 750nm which are in the yellow, orange and red spectrum. Some versions of the HPS lamp have been tuned more for vegetation and have increased blue at around the 450nm to 500nm range.
All HID lamps have a limited life, as the sodium is highly reactive it leads to a loss of gas over time this will eventually result in the lamp perishing, needing to be replaced.
The expected life span of a HPS is around 3000-5000 hours, after that time-frame they will have lost significant lumen output.