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Fluorescent lamp



Fluorescent light bulbs come in many shapes and sizes. An increasingly popular one is the compact fluorescent light bulb (CF). Many compact fluorescent lamps integrate the auxiliary electronics into the base of the lamp, allowing them to fit into a regular light bulb socket.

In the U.S., residential use of fluorescent lighting remains low (generally limited to kitchens, basements, hallways and other areas), but schools and businesses find the cost savings of fluorescents to be significant and only rarely use incandescent lights.

Lighting arrangements often use fluorescent tubes in an assortment of tints of white. In most cases this is due to failure to appreciate the difference or importance of differing tube types. Mixing tube types within fittings is also done to improve the color reproduction of low quality tubes.

In other countries, residential use of fluorescent lighting varies depending on the price of energy, financial and environmental concerns of the local population, and acceptability of the light output.

In February 2007, Australia enacted a law that will ban most sales of incandescent light bulbs by 2010.34 While the law does not specify which alternative Australians are to use, compact fluorescents are likely to be the primary replacements.

Mercury toxicity

Because fluorescent lamps contain mercury, a toxic heavy metal, governmental regulations in many areas require special disposal of fluorescent lamps, separate from general and household wastes. Mercury poses the greatest hazard to pregnant women, infants, and children.

Landfills often refuse fluorescent lamps due to their high mercury content. Households and commercial waste sources are often treated differently.

The amount of mercury in a standard lamp can vary dramatically, from 3 to 46 mg.5 A typical 2006-era four-foot (120-centimeter) T-12 fluorescent lamp (namely, F32T12) contains about 12 milligrams of mercury.6 Newer lamps contain less mercury, and the 3-4 milligram versions (such as F32T8) are sold as low-mercury types.

Cleanup of broken fluorescent lamps

A broken fluorescent tube is more hazardous than a broken conventional incandescent bulb due to the mercury content. Because of this, the safe cleanup of broken fluorescent bulbs differs from cleanup of conventional broken glass or incandescent bulbs. Ninety-nine percent of the mercury is typically contained in the phosphor, especially on lamps that are near their end of life.7 Therefore, a typical safe cleanup usually involves careful disposal of any broken glass, as well as any loose white powder (fluorescent glass coating), in accordance with local hazardous waste laws. A wet towel is normally used instead of a vacuum cleaner for cleanup of glass and powder, mainly to reduce the spread of the powder throughout the air.

Advantages over incandescent lamps

Fluorescent lamps are more efficient than incandescent light bulbs of an equivalent brightness. This is because more of the consumed energy is converted to usable light and less is converted to heat, allowing fluorescent lamps to run cooler. An incandescent lamp may convert only 10 percent of its power input to visible light. A fluorescent lamp producing as much useful visible light energy may require only one-third to one-fourth as much electricity input. Typically a fluorescent lamp will last between 10 and 20 times as long as an equivalent incandescent lamp. Where lighting is used in air-conditioned spaces, all the lamp losses must also be removed by the air conditioning equipment, resulting in a double penalty for losses due to lighting.

The higher initial cost of a fluorescent lamp is more than compensated for by lower energy consumption over its life. The longer life may also reduce lamp replacement costs, providing additional saving especially where labor is costly. Therefore it is widely used by businesses worldwide, but not so much by households.

The mercury released to the air when 5 to 45 percent of the fluorescent lamps are disposed of,8 is offset by the fact that many coal-fired electricity generators emit mercury into the air. The greater efficiency of fluorescent lamps helps to reduce powerplant emissions.


The "beat effect" problem created when shooting photos or film under standard fluorescent lighting

Fluorescent lamps require a ballast to stabilize the lamp and to provide the initial striking voltage required to start the arc discharge; this increases the cost of fluorescent luminares, though often one ballast is shared between two or more lamps. Certain types of ballasts produce audible humming or buzzing noises.

Conventional lamp ballasts do not operate on direct current. If a direct current supply with a high enough voltage to strike the arc is available, a resistor can be used to ballast the lamp but this leads to low efficiency because of the power lost in the resistor. Also, the mercury tends to migrate to one end of the tube leading to only one end of the lamp producing most of the light. Because of this effect, the lamps (or the polarity of the current) must be reversed at regular intervals.

Fluorescent lamps operate best around room temperature (say, 68 degrees Fahrenheit or 20 degrees Celsius). At much lower or higher temperatures, efficiency decreases and at low temperatures (below freezing) standard lamps may not start. Special lamps may be needed for reliable service outdoors in cold weather. A "cold start" electrical circuit was also developed in the mid-1970s.

Because the arc is quite long relative to higher-pressure discharge lamps, the amount of light emitted per unit of surface of the lamps is low, so the lamps are large compared with incandescent sources. This affects design of fixtures since light must be directed from long tubes instead of a compact source. However, in many cases low luminous intensity of the emitting surface is useful because it reduces glare.

Fluorescent lamps do not give out a steady light; instead, they flicker (fluctuate in intensity) at a rate that depends on the frequency of the driving voltage. While this is not easily discernible by the human eye, it can cause a strobe effect posing a safety hazard in a workshop for example, where something spinning at just the right speed may appear stationary if illuminated solely by a fluorescent lamp. It also causes problems for video recording as there can be a 'beat effect' between the periodic reading of a camera's sensor and the fluctuations in intensity of the fluorescent lamp. The frequency is most noticeable on CRT computer monitors set with a refresh rate similar to the frequency of the bulbs, which will appear to flicker due to the beat effect. To resolve this flicker one may change their monitor's refresh rate.

Incandescent lamps, due to the thermal inertia of their element, fluctuate less in their intensity, although the effect is measurable with instruments. This is also less of a problem with compact fluorescents, since they multiply the line frequency to levels that are not visible. Installations can reduce the stroboscope effect by using lead-lag ballasts or by operating the lamps on different phases of a polyphase power supply.

The problems with color faithfulness are discussed above.

Unless specifically designed and approved to accommodate dimming, most fluorescent light fixtures cannot be connected to a standard dimmer switch used for incandescent lamps. Two effects are responsible for this: the waveshape of the voltage emitted by a standard phase-control dimmer interacts badly with many ballasts and it becomes difficult to sustain an arc in the fluorescent tube at low power levels. Many installations require 4-pin fluorescent lamps and compatible controllers for successful fluorescent dimming; these systems tend to keep the cathodes of the fluorescent tube fully heated even as the arc current is reduced, promoting easy thermionic emission of electrons into the arc stream.

The disposal of phosphor and the small amounts of mercury in the tubes is also an environmental problem, compared with the disposal of incandescent lamps. For large commercial or industrial users of fluorescent lights, recycling services are beginning to become available.

Tube designations

Note: the information in this section might be inapplicable outside of North America.

Lamps are typically identified by a code such as F##T##, where F is for fluorescent, the first number indicates the power in watts (or strangely, length in inches in very long lamps), the T indicates that the shape of the bulb is tubular, and the last number is diameter in eighths of an inch. Typical diameters are T12 (1½ inches or 38 millimeters) for residential bulbs with old magnetic ballasts, T8 (1 inch or 25 millimeters) for commercial energy-saving lamps with electronic ballasts, and T5 (5⁄8 inches or 16 millimeters) for very small lamps which may even operate from a battery-powered device.

Slimline lamps operate on an instant start ballast and are recognizable by their single-pin bases.

High-output lamps are brighter and draw more electrical current, have different ends on the pins so they cannot be used in the wrong fixture, and are labeled F##T12HO, or F##T12VHO for very high output. Since about the early to mid 1950s to today, General Electric developed and improved the Power Groove lamp with the label F##PG17. These lamps are recognizable by their large diameter, grooved tubes.

U-shaped tubes are FB##T##, with the B meaning "bent." Most commonly, these have the same designations as linear tubes. Circular bulbs are FC##T#, with the diameter of the circle (not circumference or watts) being the first number, and the second number usually being 9 (29 mm) for standard fixtures.

Color is usually indicated by WW for warm white, EW for enhanced (neutral) white, CW for cool white (the most common), and DW for the bluish daylight white. BL is often used for blacklight (commonly used in bug zappers), and BLB for the common blacklight-blue bulbs which are dark purple. Other non-standard designations apply for plant lights or grow lights.

Philips uses numeric color codes for the colors:

  • Low color rendition
    • 33 the ubiquitous cool white (4000 Kelvin)
    • 32 warm white (3000 K)
    • 27 living room warm white (2700 K)
  • High color rendition
    • 9xy "Graphica Pro" / "De Luxe Pro" (xy00 K; eg "965" = 6500 K)
    • 8xy (xy00 K; eg "865" = 6500 K)
    • 840 cool white (4000 K)
    • 830 warm white (3000 K)
    • 827 warm white (2700 K)
  • Other
    • 09 Sun tanning lamps
    • 08 Blacklight
    • 05 Hard UV (no phosphors used at all, using an envelope of fused quartz)

Odd lengths are usually added after the color. One example is an F25T12/CW/33, meaning 25 watts, 1.5-inch diameter, cool white, 33 inches or 84 centimeters long. Without the 33, it would be assumed that an F25T12 is the more-common 30 inches long.

Compact fluorescents do not have such a designation system.

Other fluorescent lamps

Blacklights are a subset of fluorescent lamps that are used to provide long-wave ultraviolet light (at about 360-nanometer wavelength). They are built in the same fashion as conventional fluorescent lamps but the glass tube is coated with a phosphor that converts the short-wave UV within the tube to long-wave UV rather than to visible light. They are used to provoke fluorescence (to provide dramatic effects using blacklight paint and to detect materials such as urine and certain dyes that would be invisible in visible light) as well as to attract insects to bug zappers.
So-called blacklite blue lamps are also made from more expensive deep purple glass known as Wood's glass rather than clear glass. The deep purple glass filters out most of the visible colors of light directly emitted by the mercury-vapor discharge, producing proportionally less visible light compared with UV light. This allows UV-induced fluorescence to be seen more easily (thereby allowing blacklight posters to seem much more dramatic).
Sun lamps
Sun lamps contain a different phosphor that emits more strongly in medium-wave UV, provoking a tanning response in most human skin.
Grow lamps
Grow lamps contain a phosphor blend that encourages photosynthesis in plants; they usually appear pinkish to human eyes.
Germicidal lamps
Germicidal lamps contain no phosphor at all (technically making them gas discharge lamps rather than fluorescent) and their tubes are made of fused quartz that is transparent to the short-wave UV directly emitted by the mercury discharge. The UV emitted by these tubes will kill germs, ionize oxygen to ozone, and cause eye and skin damage. Besides their uses to kill germs and create ozone, they are sometimes used by geologists to identify certain species of minerals by the color of their fluorescence. When used in this fashion, they are fitted with filters in the same way as blacklight-blue lamps are; the filter passes the short-wave UV and blocks the visible light produced by the mercury discharge. They are also used in EPROM erasers.
Electrodeless induction lamps
Electrodeless induction lamps are fluorescent lamps without internal electrodes. They have been commercially available since 1990. A current is induced into the gas column using electromagnetic induction. Because the electrodes are usually the life-limiting element of fluorescent lamps, such electrodeless lamps can have a very long service life, although they also have a higher purchase price.
Cold-cathode fluorescent lamps (CCFL)
Cold-cathode fluorescent lamps are used as backlighting for liquid crystal displays in personal computer and TV monitors.

Film and video use

Special fluorescent lights are often used in film/video production. The brand name Kino Flos are used to create softer fill light and are less hot than traditional halogen light sources. These fluorescent lights are designed with special high-frequency ballasts to prevent video flickering and high color-rendition index bulbs to approximate daylight color temperatures.

Agapito Flores controversy

Many believe that a Filipino named Agapito Flores was the original inventor of the fluorescent light. It is reported that that he received a French patent for his invention and sold it to General Electric, which made millions of dollars from his idea. Flores however presented his patent to General Electric after the company had already presented the fluorescent light to the public, and much after it was originally invented.9

See also


  1. ↑ Lightsearch.com. Light Guide: Fluorescent Ballasts. Adapted from the Advanced Lighting Guidelines originally published by the California Energy Commission, 1993. Retrieved May 31, 2007.
  2. ↑ National Research Council Canada, Fluorescent Lamp Flicker. Retrieved May 31, 2007.
  3. ↑ Todd Woody, “Australia bans traditional light bulbs to combat global warming.” Green Wombat. February 20, 2007. Retrieved May 31, 2007.
  4. ↑ “World first! Australia slashes greenhouse gases from inefficient lighting.” Office of the Australian Minister for the Environmental and Water Resources. Press release (February 20, 2007). Retrieved May 31, 2007.
  5. ↑ United Nations Environment Programme, “Toolkit for identification and quantification of mercury releases.” p. 183. Retrieved May 31, 2007.
  6. ↑ Lighting Design Lab, Mercury in Fluorescent Lamps. Retrieved May 31, 2007.
  7. ↑ Floyd et al. (2002). Quoted in United Nations Environment Programme, “Toolkit for identification and quantification of mercury releases” p. 184. Retrieved February 10, 2012.
  8. ↑ United Nations Environment Programme. “Toolkit for identification and quantification of mercury releases.” p. 184. Retrieved May 31, 2007.
  9. ↑ Agapito Flores: About.com Inventors. Retrieved May 31, 2007.


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