IEC 60188: Mercury Vapor and Low-Pressure Sodium Lamps — Niche Light Sources in the LED Era

Mercury Vapor and Low-Pressure Sodium: Two “Obsolete” Light Sources Still Thriving in Niche Applications

IEC 60188 (high-pressure mercury vapour lamps) and IEC 60192 (low-pressure sodium vapour lamps) specify gas-discharge lamp performance. While LEDs have conquered general lighting, both lamp types remain irreplaceable in specific niches.

High-pressure mercury: Rich UV and blue-green spectrum — high Photosynthetically Active Radiation, making it historically the dominant plant factory light source. Drawbacks: mercury content (environmental hazard) and low color rendering (Ra≈50). Still used in UV curing and photochemical reactors.

Low-pressure sodium (SOX): Luminous efficacy up to 200 lm/W — exceeding most LEDs. Its monochromatic yellow emission (589 nm) penetrates fog exceptionally well, making it the preferred choice for tunnel, harbor, and observatory-adjacent lighting (astronomers love it because the single wavelength is easily filtered from telescope observations). The trade-off: zero color rendering (Ra=0) — everything appears greyish-yellow.

TN Lab — “Obsolete” technologies often retain unique advantages in specific niches. Low-pressure sodium at observatories is the perfect example.