"Cold Cathode" lamps are instant-start, using a large cylindrical cathode instead of a coil filament, so lamps have a long life that is unaffected by frequency of starting.
"Slimline" lamps, are also instant-start and are available in low-, high- and very high-ozone types. Their lamp life is governed by the electrode life and number of starts. Because of their high initial UVC emission, and good maintenance, Slimline UVC Germicidal Lamps are well adapted for applications such as air cooling and heating systems, conveyor lines, water sterilization and other applications that require "around-the-clock" use and therefore do not need to be turned off.
"Hot Cathode", or preheat/hot cathode, lamps generally use standard, off-the-shelf fluorescent ballasts, providing advantages in economy and space. Preheat lamps have four electrical connections per lamp and require more wiring than instant-start lamps. Frequent starts/stops will reduce the lamp life of Hot Cathode lamps.