Mercury lamps are used for outdoor lighting and large rooms, e.g. factory halls, exhibition etc.. They are discharge lamps, where there is a discharge in mercury vapor at high pressure. As a result, the discharge pole in the arc tube is itself a source of visible radiation and no phosphor is needed. The pressure in the arc tube (quartz glass tube with electrodes) reaches a value of up to several megapascals. The color of the light of mercury lamps differs significantly from daylight. The color can be improved by using tungsten filaments or appropriate phosphors. The main advantages of mercury lamps are high luminous efficiency and high luminous flux obtained from one lamp. The luminous flux of the largest units exceeds 100 000 lm, and the luminous efficiency is achieved 85 lm/W. The disadvantage of mercury vapor is the relatively high cost of the entire device due to the need to use a ballast and a capacitor. The normal life of mercury lamps is 12 000 h. The ratings for mercury lamps are given in the table.
Board. Ratings of mercury lamps
| The power of the lamp [W] | Shank type | Luminous flux [lm] type lamps | ||
| ML | HPL-N | HPL-Comfort | ||
| 50 | E 27 | – | 1800 | 2000 |
| 80 | E 27 | – | 3700 | 4100 |
| 100 | E 27 | 1100 | – | – |
| 125 | E 27 | – | 6200 | 6700 |
| 250 | E 40 | 3150 | 12700 | 14200 |
| 400 | E 40 | 5700 | 22000 | 24200 |
| 500 | E 40 | 13000 | – | – |
| 700 | E 40 | – | 38500 | – |
| 1000 | E 40 | – | 58500 | – |