A fluorescent (FL) lamp is a low-pressure mercury/argon tube with normally a phosphor coating. The mercury/argon mixture produces ultraviolet light when electricity is passed through the tube. The UV excites the phosphor and emits visible light. Today fluorescent bulbs come in many color temperatures/colors, shapes and wattages. To change the color temp all that needs to be done is use a different mix of phosphors.

The most common fluorescent lamps are the linear fluorescent bulbs. Linear FL lamps come in many different lengths and sizes. The fluorescent lamp is available in Normal Output (NO), High Output (HO), Very High Output (VHO), Compact Fluorescent (CF/PL/PC), Single Pin Instant Start (IS), and electrode-less. Each type operates at different milliamps (mA).

The FL lamp type can be identified by the markings (see glossary of terms). T-8 FL lamps are replacing T-12 lamps because the T-8 is more efficient. In North America a T-8 four foot bulb is normally 32-watts and needs a T-8 ballast to operate properly. In Europe the T-8 conversion bulb is 36-watts and operates on T-12 ballasts. It is important to match the wattage and type of bulb with the proper ballast. Soon the T-8s are going to be replaced with T-5 bulbs but these bulbs need different fixtures because the sockets are not the same. These bulbs are becoming popular because of its compact size and high efficiency.

Compact Fluorescent / Power Compact fluorescent (CF/PC) lamps are usually linear lamps but they are normally bent into a U shape. The most common types are the compacts that replace incandescent lamps. These lamps have the ballast built in and have a medium screw socket. The T-5 (not T-5 linear) compact FL bulbs with 4 pins on one end are being used for a wide range of places (office lighting, home lighting, retail lighting, commercial lighting, aquarium lighting). Some of the CF/PC lamps should only be operated on RS ballasts and not on IS ballasts. It is important to match the bulb type with the right ballast. If someone is not certain what combination of lamps and ballasts to use please contact the manufacturers. Some CF/PC lamps have glow starter switches built in. These CF/PC bulbs usually have 2 pins (pre-heat) and are not dimmable. 2 pin lamps should only be operated on mag. ballasts.

These lamps operate by using a magnetic field and no electrodes. When a lamp does not have any electrodes to wear out the lamp lasts many years. Electrode-less lamps are great alternatives for HPS and MH lamps.