Fluorescent lamps were introduced in the 1930s. They use a ballast to feed electricity through glass tubes filled with gas and a small amount of mercury, creating UV light that turns visible when it hits a phosphor coating on the inside of the tube. The newer electronic ballasts have replaced the magnetic ballasts, eliminating the former problems of slow startup, flickering, and humming. Fluorescent lamps, in general, are more efficient than incandescent lamps, last longer, and operate cooler. Fluorescent lamps contain a small amount of mercury so should be recycled properly. You will find three styles of fluorescent lamps on the market:

• Tube—This was the first style of fluorescent lamp and they now come in a variety of sizes. Tubes are excellent for ambient or some task lighting, they can be dimmed, and they last around 10,000 hours. For many locations, it is important to pay attention to the lamp’s color temperature and CRI.

• compact fluorescent lamps (cFL)—CFLs (see Figure 7.17) use the same fluorescent technol­ogy only the tube is designed into a compact style, the now familiar corkscrew style. This style has a screw-type base so they can be used in fixtures to replace some incandescent lamps. Dimmable lamps are available and compact fluorescents come in different color temperature and CRI ratings. The ballast for these lamps is contained in the lamp base and they last around 10,000 hours. Compact fluorescents are also available with a glass bulb around them to make them appear the same as incandescent lamps, which is a good alternative if your client does not like the appearance of the corkscrew lamp. Be aware that some compact fluorescent lamps take time to warm up so when they are first turned on they are very dim, but after a period of time achieve their full brightness. This too may not be popular with your client.

• Circline—These fluorescent lamps are built with the tube forming a circle or ring. They operate like other fluorescent tubes and are designed to fit in many center room light fixtures for ambi­ent lighting.