Fluorescent lamp

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=20

Fluorescent lamps in Shinbashi, Tokyo, Japan

=20

Assorted types of fluorescent lamps. Top, two Compact = fluorescent=20 lamps, bottom, two regular tubes. Matchstick shown for=20 scale.

A fluorescent lamp is a gas-discharge = lamp=20 that uses electricity to = excite mercury = vapor in = argon or = neon gas, resulting in a = plasma = that=20 produces short-wave ultraviolet light. = This=20 light then causes a phosphor to fluoresce, = producing visible = light.

Unlike incandescent = lamps,=20 fluorescent lamps always require a ballast to = regulate=20 the flow of power through the lamp. In common tube fixtures (typically 4 = ft (120=20 cm) or 8 ft (240 cm) in length), the ballast is enclosed in the fixture. = Comp= act=20 fluorescent light bulbs may have a conventional ballast located in = the=20 fixture or they may have ballasts integrated in the bulbs, allowing them = to be=20 used in lampholders normally used for incandescent lamps.

1 History=20
2 Principles of=20 operation=20
- 2.1 Mechanism = of light=20 production=20
- 2.2 Electrical = aspects of=20 operation=20
- 2.3 Flicker=20
- 2.4 Efficiency=20
- 2.5 Method of = 'starting' a=20 fluorescent lamp=20
- 2.6 Mechanisms = of lamp=20 failure at end of life=20
  
  2.6.1 Emission mix runs=20 out=20
  2.6.2 Failure = of integral=20 ballast electronics=20
  2.6.3 Failure = of the=20 phosphor=20
  2.6.4 Tube = runs out of=20 mercury
- 2.7 Phosphors = and the=20 spectrum of emitted light
3 Usage=20
4 Mercury = toxicity=20
5 Cleanup of = broken=20 fluorescent lamps=20
6 Advantages over = incandescent lamps=20
7 Disadvantages=20
- 7.1 Ultraviolet = light=20
- 7.2 Ballasts=20
- 7.3 Power = factor=20
- 7.4 Power=20 harmonics=20
- 7.5 Optimum = operating=20 temperature=20
- 7.6 Non-compact = light=20 source=20
- 7.7 Flicker=20 problems=20
- 7.8 Color=20 rendition=20
- 7.9 Dimming=20
- 7.10 Disposal = and=20 recycling
8 Tube=20 designations=20
9 Other = fluorescent=20 lamps=20
10 Science=20 demonstrations=20
11 Film and video = use=20
12 See = also=20
13 References=20
14 External = links=20

[edit]=20 History

The earliest ancestor of the fluorescent lamp is probably the device = by Heinrich = Geissler who,=20 in 1856, obtained a bluish glow from a gas which was sealed in a tube = and=20 excited with an induction = coil.

At the 1893 World's Fair, = the World = Columbian=20 Exposition in Chicago, Illinois displayed Nikola=20 Tesla's fluorescent lights.

In 1894, D. McFarlane = Moore=20 created the Moore lamp, a commercial gas discharge = lamp=20 meant to compete with the incandescen= t light=20 bulb of his former boss Thomas Edison. = The gases=20 used were nitrogen and carbon=20 dioxide emitting respectively pink and white light, and had moderate = success.

In 1901, Peter Cooper = Hewitt=20 demonstrated the mercury-vapor lamp, which emitted light of a blue-green = color,=20 and thus was unfit for most practical purposes. It was, however, very = close to=20 the modern design, and had much higher efficiency than incandescent = lamps.

In 1926, Edmund Germer = and=20 coworkers proposed to increase the operating pressure within the tube = and to=20 coat the tube with fluorescent = powder which=20 converts ultraviolet light = emitted by=20 an excited plasma into more uniformly white-colored light. Germer is = today=20 recognized as the inventor of the fluorescent lamp.

General = Electric later=20 bought Germer's patent and under the direction of George=20 E. Inman brought the fluorescent lamp to wide commercial use by = 1938.

[edit]=20 Principles of operation

The main principle of fluorescent tube operation is based around inelastic=20 scattering of electrons. An incident electron (emitted from the = coating on=20 the coils of wire forming the cathode electrode) = collides with=20 an atom in the gas (such as mercury, argon or krypton) used as the = ultraviolet=20 emitter. This causes an electron in the atom to temporarily jump up to a = higher=20 energy=20 level to absorb some, or all, of the kinetic energy = delivered=20 by the colliding electron. This is why the collision is called = 'inelastic' as=20 some of the energy is absorbed. This higher energy state is unstable, = and the=20 atom will emit an ultraviolet photon as the atom's = electron=20 reverts to a lower, more stable, energy level. The photons that are = released=20 from the chosen gas mixtures tend to have a wavelength in the = ultraviolet part=20 of the spectrum. This is not visible to the human eye, so must be = converted into=20 visible light. This is done by making use of fluorescence. = This=20 fluorescent conversion occurs in the phosphor coating on the inner = surface of=20 the fluorescent tube, where the ultraviolet photons are absorbed by = electrons in=20 the phosphor's atoms, causing a similar energy jump, then drop, with = emission of=20 a further photon. The photon that is emitted from this second = interaction has a=20 lower energy than the one that caused it. The chemicals that make up the = phosphor are specially chosen so that these emitted photons are at = wavelengths=20 visible to the human eye. The difference in energy between the absorbed=20 ultra-violet photon and the emitted visible light photon goes to heat up = the=20 phosphor coating.

[edit]=20 Mechanism of light production

=20

Close-up of the cathodes and anodes of a germicidal = lamp (an=20 essentially-similar design that uses no fluorescent phosphor, allowing = the=20 electrodes to be seen.)

=20

The unfiltered ultraviolet glow of a germicidal = lamp is=20 produced by a low pressure mercury vapor discharge (identical to that in = a=20 fluorescent lamp) in an uncoated fused quartz = envelope.

A fluorescent lamp is filled with a gas containing low = pressure mercury=20 vapor and argon (or=20 xenon), = or more=20 rarely argon-neon, or=20 sometimes even krypton. The inner = surface of=20 the bulb is coated with a fluorescent (and = often=20 slightly phosphorescent) = coating=20 made of varying blends of metallic and rare-earth phosphor salts. The bulb's cathode = is=20 typically made of coiled tungsten which is = coated with a=20 mixture of barium, strontium and calcium oxides (chosen to have a = relatively low=20 thermionic = emission=20 temperature). When the light is turned on, the electric power heats up = the=20 cathode enough for it to emit electrons. These electrons collide with = and ionize=20 noble gas=20 atoms in the bulb surrounding the filament to form a plasma by = a process=20 of impact = ionization. As=20 a result of avalanche = ionization,=20 the conductivity of the ionized gas rapidly rises, allowing higher = currents to=20 flow through the lamp. The mercury, which exists at a stable vapour = pressure=20 equilibrium point of about one part per thousand in the inside of the = tube (with=20 the noble gas pressure typically being about 0.3% of stand= ard=20 atmospheric pressure), is then likewise ionized, causing it to emit = light in=20 the ultraviolet (UV) = region of=20 the spectrum predominantly at wavelengths of = 253.7 nm and 185=20 nm. The efficiency of fluorescent lighting owes much to the fact that = low=20 pressure mercury discharges emit about 65% of their total light at the = 254 nm=20 line (also about 10-20% of the light emitted in UV is at the 185 nm = line). The=20 UV light is absorbed=20 by the bulb's fluorescent coating, which re-radiates the energy at = lower=20 frequencies (longer wavelengths: two intense lines of 440nm and 546nm = wavelength=20 appear on commercial fluorescent tubes) (see stokes shift) to = emit visible=20 light. The blend of phosphors controls the color of the light, and = along with=20 the bulb's glass=20 prevents the harmful UV light from escaping.

[edit]=20 Electrical aspects of operation

Fluorescent lamps are negative = resistance=20 devices, so as more current flows through them (more gas ionized), the=20 electrical resistance of the fluorescent lamp drops, allowing even more = current=20 to flow. Connected directly to a constant-voltage mains power = line, a=20 fluorescent lamp would rapidly self-destruct due to the uncontrolled = current=20 flow. To prevent this, fluorescent lamps must use an auxiliary device, = commonly=20 called a ballast, to = regulate=20 the current flow through the tube.

While the ballast could be (and occasionally is) as simple as a resistor,=20 substantial power is wasted in a resistive ballast so ballasts usually = use a reactance (inductor or capacitor)=20 instead. For operation from AC mains voltage, the use of simple inductor = (a=20 so-called "magnetic=20 ballast") is common. In countries that use 120 V AC mains, = the mains=20 voltage is insufficient to light large fluorescent lamps so the ballast = for=20 these larger fluorescent lamps is often a step-up autotransformer = with=20 substantial leakage = inductance=20 (so as to limit the current flow). Either form of inductive ballast may = also=20 include a capacitor for power = factor=20 correction.

In the past, fluorescent lamps were occasionally run directly from a = DC=20 supply of sufficient voltage to strike an arc. In this case, there was = no=20 question that the ballast must have been resistive rather than reactive, = leading=20 to power losses in the ballast resistor. Also, when operated directly = from DC,=20 the polarity of the supply to the lamp must be reversed every time the = lamp is=20 started; otherwise, the mercury accumulates at one end of the tube. = Nowadays,=20 fluorescent lamps are essentially never operated directly from DC; = instead, an=20 inverter converts the DC into AC and provides the current-limiting = function as=20 described below for electronic ballasts.

More sophisticated ballasts may employ transistors or = other semiconductor = components=20 to convert mains voltage into high-frequency AC while = also=20 regulating the current flow in the lamp. These are referred to as "electronic=20 ballasts".

[edit]=20 Flicker

Fluorescent lamps which operate directly from mains frequency AC will = flicker=20 at twice the mains frequency, since the power being delivered to the = lamp drops=20 to zero twice per cycle. This means the light flickers at 120 times per = second=20 (Hz) in countries which use 60-cycle-per-second (60 Hz) AC, and 100 = times=20 per second in those which use 50 Hz. This same principle can also = cause hum=20 from fluorescent lamps, actually from its ballast. Both the annoying hum = and=20 flicker are eliminated in lamps which use a high-frequency electronic = ballast,=20 such as the increasingly popular compact = fluorescent=20 bulb.

In some circumstances, fluorescent lamps operated at mains frequency = can also=20 produce flicker at the mains frequency (50 or 60 Hz) itself, which = is=20 noticeable by more people. This can happen in the last few hours of tube = life=20 when the cathode emission coating at one end is almost run out, and that = cathode starts=20 having difficulty emitting enough electrons into the = gas fill,=20 resulting in slight rectification and = hence uneven=20 light output in positive and negative going mains cycles. Mains = frequency=20 flicker can also sometimes be emitted from the very ends of the tubes, = as a=20 result of each tube electrode alternately operating as an anode and cathode each half = mains cycle,=20 and producing slightly different light output pattern in anode or = cathode mode.=20 (This was a more serious issue with tubes over 40 years ago, and many = fittings=20 of that era shielded the tube ends from view as a result.) Flicker at = mains=20 frequency is more noticeable in the peripheral = vision than=20 it is in the center of gaze.

[edit]=20 Efficiency

The efficiency of fluorescent tubes ranges from about 16 lumens/watt = for a 4=20 watt tube with an ordinary ballast to as high as about 95 lumens/watt = for a 32=20 watt tube with modern electronic ballast, commonly averaging 50 to 67 = lm/W=20 overall. Most compact fluorescents 13 watts or more with integral = electronic=20 ballasts achieve about 60 lumens/watt. Due to phosphor degradation as = they age,=20 the average brightness over the entire service life is actually about = 10%=20 less.[1]

[edit]=20 Method of 'starting' a fluorescent = lamp

=20

A preheat fluorescent lamp circuit using an = automatic=20 starting switch

=20

A preheat fluorescent lamp "starter" = (automatic=20 starting switch)

The mercury atoms in the fluorescent tube must be ionized before the = arc can=20 "strike" within the tube. For small lamps, it does not take much voltage = to=20 strike the arc and starting the lamp presents no problem, but larger = tubes=20 require a substantial voltage (in the range of a thousand volts).

In some cases, that is exactly how it is done: instant start=20 fluorescent tubes simply use a high enough voltage to break down the gas = and=20 mercury column and thereby start arc conduction. These tubes can be = identified=20 by the facts that

they have a single pin at each end of the tube and=20
the lampholders that they fit into have a "disconnect" socket at = the=20 low-voltage end to ensure that the mains current is automatically = removed so=20 that a person replacing the lamp cannot receive a high-voltage electric = shock.=20

In other cases, a separate starting aid must be provided. Some = fluorescent=20 designs (preheat lamps) use a combination filament/cathode at each end of = the lamp=20 in conjunction with a mechanical or automatic switch (see photo) that = initially=20 connect the filaments in series with the ballast and thereby preheats = the=20 filaments prior to striking the arc.

These systems are standard equipment in 240 V countries, and = generally use a=20 glowstarter. Before the 1960s, four-pin thermal starters and manual = switches=20 were also used. Electronic starters are also sometimes used with these=20 electromagnetic ballast fittings.

During preheating, the filaments emit electrons into the gas column = by thermionic = emission,=20 creating a glow discharge = around the=20 filaments. Then, when the starting switch opens, the inductive ballast = and a=20 small value capacitor across the starting switch create a high voltage = which=20 strikes the arc. Tube strike is reliable in these systems, but = glowstarters will=20 often cycle a few times before letting the tube stay lit, which causes=20 objectionable flashing during starting. The older thermal starters = behaved=20 better in this respect.

Once the tube is struck, the impinging main discharge then keeps the=20 filament/cathode hot, permitting continued emission.

If the tube fails to strike, or strikes then extinguishes, the = starting=20 sequence is repeated. With automated starters such as glowstarters, a = failing=20 tube will thus cycle endlessly, flashing time and time again as the = starter=20 repeatedly starts the worn-out lamp, and the lamp then quickly goes out = as=20 emission is insufficient to keep the cathodes hot, and lamp current is = too low=20 to keep the glowstarter open. This causes visually unpleasant frequent = bright=20 flashing and runs the ballast at above design temperature. Turning the=20 glowstarter a quarter turn anticlockwise will disconnect it, opening the = circuit.

Some more advanced starters time out in this situation, and do not = attempt=20 repeated starts until power is reset. Some older systems used a thermal=20 overcurrent trip to detect repeated starting attempts. These require = manual=20 reset.

Newer rapid start ballast designs provide filament power = windings=20 within the ballast; these rapidly and continuously warm the = filaments/cathodes=20 using low-voltage AC. No inductive voltage spike is produced for = starting, so=20 the lamps must usually be mounted near a grounded (earthed) reflector to = allow=20 the glow discharge to propagate through the tube and initiate the arc=20 discharge.

Electronic ballasts often revert to a style in-between the preheat = and=20 rapid-start styles: a capacitor (or sometimes an autodisconnecting = circuit) may=20 complete the circuit between the two filaments, providing filament = preheating.=20 When the tube lights, the voltage and frequency across the tube and = capacitor=20 typically both drop, thus capacitor current falls to a low but non-zero = value.=20 Generally this capacitor and the inductor, which provides current = limiting in=20 normal operation, form a resonant circuit, = increasing=20 the voltage across the lamp so it can easily start.

Some electronic ballasts use programmed start. The output AC frequency is=20 started above the resonance frequency of the output circuit of the = ballast; and=20 after the filaments are heated, the frequency is rapidly decreased. If = the=20 frequency approaches the resonant = frequency of=20 the ballast, the output voltage will increase so much that the lamp will = ignite.=20 If the lamp does not ignite, an electronic circuit stops the operation = of the=20 ballast.

[edit]=20 Mechanisms of lamp failure at end of = life

The end of life failure mode for fluorescent lamps varies depending = how you=20 use them and their control gear type. There are three main failure modes = currently, and a fourth which is starting to appear:

[edit]=20 Emission mix runs out

=20

Closeup of the filament on a low pressure mercury = gas=20 discharge lamp showing white thermionic emission mix coating on the = central=20 portion of the coil. Typically made of a mixture of barium, strontium and calcium oxides, the = coating is=20 sputtered away through normal use, often eventually resulting in lamp=20 failure.

The "emission mix" on the tube filaments/cathodes is necessary to = enable=20 electrons to pass into the gas via thermionic = emission=20 at the tube operating voltages used. The mix is slowly sputtered off by=20 bombardment with electrons and mercury ions during operation, but a = larger=20 amount is sputtered off each time the tube is started with cold = cathodes. (The=20 method of starting the lamp and hence the control gear type has a = significant=20 impact on this.) Lamps operated for typically less than 3 hours each = switch-on=20 will normally run out of the emission mix before other parts of the lamp = fail.=20 The sputtered emission mix forms the dark marks at the tube ends seen in = old=20 tubes. When all the emission mix is gone, the cathode cannot pass = sufficient=20 electrons into the gas fill to maintain the discharge at the designed = tube=20 operating voltage. Ideally, the control gear should shut down the tube = when this=20 happens. However, some control gear will provide sufficient increased = voltage to=20 continue operating the tube in cold cathode = mode, which=20 will cause overheating of the tube end and rapid disintegration of the=20 electrodes and their support wires until they are completely gone or the = glass=20 cracks, wrecking the low pressure gas fill and stopping the gas = discharge.

[edit]=20 Failure of integral ballast = electronics

This is only relevant to compact = fluorescent=20 lamps with integral electrical = ballasts.=20 Ballast electronics failure is a somewhat random process which follows = the=20 standard failure profile for any electronic devices. Integral electronic = ballasts suffer from shortened lifespans in high humidity applications. = There is=20 an initial small peak of early failures, followed by a drop and steady = increase=20 over lamp life. Life of electronics is heavily dependent on operating=20 temperature=E2=80=94it typically halves for each 10 =C2=B0C temperature = rise. The quoted=20 average life of a lamp is usually at 25 =C2=B0C ambient (this may vary = by country).=20 The average life of the electronics at this temperature is normally = greater than=20 this, so at this temperature, not many lamps will fail due to failure of = the=20 electronics. In some fittings, the ambient temperature could be well = above this,=20 in which case failure of the electronics may become the predominant = failure=20 mechanism. Similarly, running a compact fluorescent lamp base-up will = result in=20 hotter electronics and shorter average life (particularly with higher = power=20 rated ones). Electronic ballasts should be designed to shut down the = tube when=20 the emission mix runs out as described above. In the case of integral = electronic=20 ballasts, since they never have to work again, this is sometimes done by = having=20 them deliberately burn out some component to permanently cease = operation.

[edit]=20 Failure of the phosphor

The phosphor drops off in efficiency during use. By around 25,000 = operating=20 hours, it will typically be half the brightness of a new lamp (although = some=20 manufacturers claim much longer half-lives for their lamps). Lamps which = do not=20 suffer failures of the emission mix or integral ballast electronics will = eventually develop this failure mode. They still work, but have become = dim and=20 inefficient. The process is slow, and often only becomes obvious when a = new lamp=20 is operating next to an old lamp.

[edit]=20 Tube runs out of mercury

Mercury is lost from the gas fill throughout the lamp life, as it is = slowly=20 absorbed into glass, phosphor, and tube electrodes, where it can no = longer=20 function. Historically this hasn't been a problem because tubes have had = an=20 excess of mercury. However, environmental concerns are now resulting in = low=20 mercury content tubes which are much more accurately dosed with just = enough=20 mercury to last the expected life of the lamp. This means that loss of = mercury=20 will take over from failure of the phosphor in some lamps. The failure = symptom=20 is similar, except loss of mercury initially causes an extended run-up = time=20 (time to reach full light output), and finally causes the lamp to glow a = dim=20 pink when the mercury runs out and the argon base gas takes over as the = primary=20 discharge.

[edit]=20 Phosphors and the spectrum of emitted = light

Some people find the color spectrum = produced=20 by some fluorescent lamps to be harsh and displeasing. A healthy person = can=20 sometimes appear to have an unhealthy skin tone under fluorescent = lighting. The=20 extent to which this phenomenon occurs is related to the light's color = rendering=20 index (CRI).

CRI is a measure of how well balanced the different color components = of the=20 white light are. By definition, an incandescent lamp has a CRI of 100. = Real life=20 fluorescent tubes achieve CRIs of anywhere from 50% to 99%. Fluorescent = lamps=20 with low CRI have phosphors which emit too little red light. Skin = appears less=20 pink and unhealthy compared to incandescent lighting. Colored objects = appear=20 muted. For example a low CRI 6800K halophosphate tube, which is about as = visually unpleasant as they get, will make reds appear dull red or = brown.

CCT Color = temperature is a=20 measure of the whiteness of a light source. Typical incandescent = lighting is=20 2700K which is yellowish-white. Halogen lighting is 3000K. Fluorescent = lamps are=20 manufactured to a chosen CCT by altering the mixture of phosphors inside = the=20 tube. Warm-white fluorescents have CCT of 2700K and are popular for = residential=20 lighting. Neutral-white fluorescents have a CCT of 3000K or 3500K. = Cool-white=20 fluorescents have a CCT of 4100K and are popular for office lighting. = Daylight=20 fluorescents have a CCT of 5000K to 6500K, which is bluish-white.

High CCT lighting generally requires higher light levels. At dimmer=20 illumination levels, the human eye perceives lower color temperatures as = more=20 natural. So, a dim 2700K incandescent lamp appears natural, and a bright = 5000K=20 lamp also appears natural, but a dim 5000K fluorescent lamp appears too = pale.=20 Daylight-type fluorescents look natural only if they are very = bright.

Some of the least pleasant light comes from tubes containing the = older halophosphate=20 type phosphors (chemical = formula Ca₅(PO₄)_{3(F,Cl):Sb³⁺,Mn²⁺). =
The bad=20
color reproduction is due to the fact that this phosphor mainly emits =
yellow and=20
blue light, and relatively little green and red. To the eye, this =
mixture=20
appears white, but the light has an incomplete spectrum. The CRI of =
such lamps=20
is only 60.}

Since the 1990s, higher quality fluorescent lamps use either a higher = CRI=20 halophosphate coating, or a triphosphor mixture, based on europium and terbium ions, that=20 have emission bands more evenly distributed over the spectrum of visible = light.=20 High CRI halophosphate and triphosphor tubes give a more natural color=20 reproduction to the human eye. The CRI of such lamps is typically = 82-100.

At least some of the early fluorescent lamps used compounds = containing=20 beryllium, a toxic element. However, it's very unlikely that one would = encounter=20 any such lamps.

Fluorescent lamp spectra
Typical fluorescent lamp with "rare = earth"=20 phosphor		A typical "cool white" fluorescent lamp utilizing two rare earth = doped=20 phosphors, Tb³⁺, Ce³⁺:LaPO₄ for = green and blue emission and Eu:Y₂O₃ for red. = For an=20 explanation of the origin of the individual peaks click on the = image. Note=20 that several of the spectral peaks are directly generated from the = mercury=20 arc. This is likely the most common type of fluorescent lamp in = use=20 today.
An older style halophosphate=20 phosphor fluorescent lamp		Halophosphate phosphors in these lamps usually consist of = trivalent antimony=20 and divalent manganese = doped calcium=20 halophosphate (Ca₅(PO₄)₃(Cl,F):Sb³⁺,=20 Mn²⁺). The color of the light output can be adjusted by = altering the ratio of the blue emitting antimony dopant and orange = emitting manganese dopant. The color rendering ability of these = older=20 style lamps is quite poor. Halophosphate phosphors were invented = by A.H.=20 McKeag et al. in 1942.
"Natural sunshine" fluorescent light		An explanation of the origin of the peaks is on the image = page.
Yellow fluorescent lights		The spectrum is nearly identical to a normal fluorescent bulb = except=20 for a near total lack of light below 500 nanometers. This effect = can be=20 achieved through either specialized phosphor use or more commonly = by the=20 use of a simple yellow light filter. These lamps are commonly used = as=20 lighting for photolithography=20 work in cleanrooms = and as "bug=20 repellant" outdoor lighting (the efficacy of which is = questionable).
Spectrum of a "blacklight" = bulb		There is typically only one phosphor present in a blacklight = bulb,=20 usually consisting of europium-doped = strontium fluoroborate=20 which is contained in an envelope of Wood's=20 glass.

[edit]=20 Usage

Fluorescent light bulbs come in many shapes and sizes. An = increasingly=20 popular one is the comp= act=20 fluorescent light bulb (CF). Many compact fluorescent lamps = integrate the=20 auxiliary electronics into the base of the lamp, allowing them to fit = into a=20 regular light bulb socket.

In the US, residential use of = fluorescent lighting remains low (generally limited to kitchens, basements, hallways and other = areas), but schools = and businesses find=20 the cost savings of fluorescents to be significant and only rarely use=20 incandescent lights.

Lighting arrangements often use fluorescent tubes in an assortment of = tints=20 of white. Sometimes this is done due to failure to appreciate the = difference or=20 importance of differing tube types. Mixing tube types within fittings is = also=20 sometimes done to improve the color reproduction of lower quality tubes. = Use is=20 substantially higher and increasing in places such as California, where = tax=20 incentives exist, and environmental awareness are relatively high.

In other countries, residential use of fluorescent lighting varies = depending=20 on the price of energy, financial and environmental concerns of the = local=20 population, and acceptability of the light output. In East and Southeast = Asia it=20 is very rare to see incandescent = bulbs in=20 buildings anywhere.

In February 2007, Australia enacted a = law that=20 will ban most sales of incandescent light bulbs by 2010 [2] [3]. While the law does not specify which alternative = Australians are to use, compact fluorescents are likely to be the = primary=20 replacements. In April 2007, Canada announced a similar plan to phase = out the=20 sale of incandescent bulbs by 2012.[4].

[edit]=20 Mercury toxicity

Because fluorescent lamps contain mercury, = a toxic heavy=20 metal, governmental regulations in many areas require special = disposal of=20 fluorescent lamps, separate from general and household wastes. Mercury = poses the=20 greatest hazard to pregnant women, infants, and children.

Landfills often refuse fluorescent lamps due to their high mercury = content.=20 Households and commercial waste sources are often treated = differently.

The amount of mercury in a standard lamp can vary dramatically, from = 3 to 46=20 mg. ^[1]=20 Newer lamps contain less mercury and the 3-4 mg versions are sold as = low-mercury=20 types. (A typical 2006-era 4 ft (120 cm) T-12 fluorescent lamp (i.e., = F32T12)=20 contains about 12 milligrams of = mercury[2].)

In early 2007, the National Electrical Manufacturers Association in = the US=20 announced that "Under the voluntary commitment, effective April 15, = 2007,=20 participating manufacturers will cap the total mercury content in CFLs = under 25=20 watts at 5 milligrams (mg) per unit. CFLs that use 25 to 40 watts of = electricity=20 will have total mercury content capped at 6 mg per unit."NEMA Voluntary Commitment on Mercury in CFLs

[edit]=20 Cleanup of broken fluorescent = lamps

A broken fluorescent tube is more hazardous than a broken = conventional=20 incandescent bulb due to the mercury content. Because of this, the safe = cleanup=20 of broken fluorescent bulbs differs from cleanup of conventional broken = glass or=20 incandescent bulbs. 99% of the mercury is typically contained in the = phosphor,=20 especially on lamps that are near their end of life ^[3].=20 Therefore, a typical safe cleanup usually involves first opening a = window and=20 then leaving the room (restricting access) for at least 15 minutes, = wearing=20 gloves carefully dispose of any broken glass, as well as any loose white = powder=20 (fluorescent glass coating). You can use sticky tape to pick up small = pieces...=20 double bag any waste. Dispose of waste in accordance with local = hazardous waste=20 laws. Finally a wet paper towel should be used instead of a vacuum = cleaner for=20 cleanup of glass and powder, to reduce the vaporization of the mercury = into the=20 air.

The first time you vacuum the area where the bulb was broken, remove = the=20 vacuum bag once done cleaning the area (or empty and wipe the canister) = and put=20 the bag and/or vacuum debris, as well as the cleaning materials, in two = sealed=20 plastic bags in the outdoor trash or protected outdoor location for = normal=20 disposal [5]

It would be safer to use a vacuum cleaner with a HEPA filter, because = older-type vacuum cleaners don't trap really-fine dust. That dust is = exhausted=20 into the room, which spreads it.

Fluorescent lamps manufactured many decades ago had phosphors that = contained=20 beryllium, which is toxic. One is not likely to encounter lamps this = old.

What = to Do if a=20 Fluorescent Light Bulb Breaks

[edit]=20 Advantages over incandescent lamps

Fluorescent lamps are more efficient = than incandescen= t light=20 bulbs of an equivalent brightness. This is because a greater = proportion of=20 the power used is converted to usable light and a smaller = proportion is=20 converted to heat,=20 allowing fluorescent lamps to run cooler. A typical 100 Watt tungsten = filament=20 incandescent lamp may convert only 2.6% of its power input to visible = light,=20 whereas typical fluorescent lamps convert between 6.6% and 15.2% of = their power=20 input to visible light - see the table in the luminous = efficacy=20 article. Typically a fluorescent lamp will last between 10 to 20 times = as long=20 as an equivalent incandescent lamp.^{[citation=20
needed]}

The higher initial cost of a fluorescent lamp is usually more than=20 compensated for by lower energy consumption over its life. The longer = life may=20 also reduce lamp replacement costs, providing additional saving = especially where=20 labour is costly. Therefore it is widely used by businesses worldwide, = but not=20 so much by households.

=20

The "beat effect" problem created when shooting = photos or=20 film under standard fluorescent lighting.

[edit]=20 Disadvantages

[edit]=20 Ultraviolet light

Fluorescent lamps can cause problems among individuals with = pathological=20 sensitivity to ultraviolet light. They can induce disease activity in=20 photosensitive individuals with System= ic lupus=20 erythematosus; standard acrylic diffusers absorb UV-B radiation and = appear=20 to protect against this.^[4]=20 In rare cases individuals with solar urticaria (allergy = to=20 sunlight) can get a rash from fluorescent lighting.^[5]

[edit]=20 Ballasts

Fluorescent lamps require a ballast to stabilize the lamp and to = provide the=20 initial striking voltage required to start the arc discharge. This = increases the=20 cost of fluorescent luminaires, though = often one=20 ballast is shared between two or more lamps. Electromagnetic ballasts = with a=20 minor fault can produce an audible humming or buzzing noise.

Conventional lamp ballasts do not operate on direct current. If a = direct=20 current supply with a high enough voltage to strike the arc is = available, a=20 resistor can be used to ballast the lamp but this leads to low = efficiency=20 because of the power lost in the resistor. Also, the mercury tends to = migrate to=20 one end of the tube leading to only one end of the lamp producing most = of the=20 light. Because of this effect, the lamps (or the polarity of the = current) must=20 be reversed at regular intervals.

[edit]=20 Power factor

Fluorescent lamp ballasts have a power factor of = less than=20 unity. For large installations, this makes the provision of electrical = power=20 more expensive as special measures need to be taken to bring the power = factor=20 closer to unity.

[edit]=20 Power harmonics

Fluorescent lamps are a non-linear load and generate harmonics on the = 50 Hz or 60 Hz sinusoidal waveform of the electrical power = supply.=20 This can generate radio frequency noise in some cases. Suppression of = harmonic=20 generation is standard practice, but imperfect. Very good suppression is = possible, but adds to the cost of the fluorescent fixtures.

[edit]=20 Optimum operating temperature

Fluorescent lamps operate best around room temperature (say, = 20 =C2=B0C or=20 68 =C2=B0F). At much lower or higher temperatures, efficiency = decreases and at=20 low temperatures (below freezing) standard lamps may not start. Special = lamps=20 may be needed for reliable service outdoors in cold weather. A "cold = start"=20 electrical circuit was also developed in the mid-1970s.

[edit]=20 Non-compact light source

Because the arc is quite long relative to higher-pressure discharge = lamps,=20 the amount of light emitted per unit of surface of the lamps is low, so = tube=20 lamps were large compared with incandescent sources. However, in many = cases low=20 luminous intensity of the emitting surface was useful because it reduced = glare. The = bulk=20 created by this lamp affected the design of fixtures since light must be = directed from long tubes instead of a compact source.

Recently, a new type of fluorescent lamp, the CFL, = has been=20 introduced to address this issue and allow regular incandescent sockets = to be=20 fitted with this type of lamp, thereby negating the need to mount it on = special=20 fixtures. However, some CFLs intended to replace incandescents will not = fit some=20 desk lamps, because the harp (heavy wire shade support bracket) is = shaped for=20 the narrow neck of an incandescent lamp. CFLs tend to have a wide = housing for=20 their electronic ballast close to the lamp's base, too wide to fit.

[edit]=20 Flicker problems

Fluorescent fittings using a magnetic mains frequency ballast do not = give out=20 a steady light; instead, they flicker (fluctuate in intensity) at twice = the=20 supply frequency. While this is not easily discernible by the human eye, = it can=20 cause a strobe = effect posing a=20 safety hazard in a workshop for example, where something spinning at = just the=20 right speed may appear stationary if illuminated solely by a fluorescent = lamp.=20 It also causes problems for video recording as there can be a 'beat = effect'=20 between the periodic reading of a camera's sensor and the fluctuations = in=20 intensity of the fluorescent lamp.

Incandescent = lamps,=20 due to the thermal = inertia of their=20 element, fluctuate to a lesser extent. This is also less of a problem = with=20 compact fluorescents, since they multiply the line frequency to levels = that are=20 not visible. Installations can reduce the stroboscope effect = by using=20 lead-lag ballasts, by operating the lamps on different phases of a polyphase=20 power supply, or by use of electronic ballasts.

Electronic ballasts do not produce light flicker, since the phosphor=20 persistence is longer than a half cycle of the higher operation = frequency.

The non-visible 100=E2=80=93120 Hz flicker from fluorescent = tubes powered by=20 magnetic ballasts is associated with headaches and eyestrain. = Individuals with=20 high flicker = fusion=20 threshold are particularly affected by magnetic ballasts: their EEG = alpha=20 waves are markedly attenuated and they perform office tasks with greater = speed=20 and decreased accuracy. The problems are not observed with electronic=20 ballasts.^[6]=20 Ordinary people have better reading performance using high-frequency=20 (20=E2=80=9360 kHz) electronic ballasts than magnetic ballasts.^[7]

The flicker of fluorescent lamps, even with magnetic ballasts, is so = rapid=20 that it is unlikely to present a hazard to individuals with epilepsy.^[8]=20 Early studies suspected a relationship between the flickering of = fluorescent=20 lamps with magnetic ballasts and repetit= ive=20 movement in autistic = children.[9]=20 However, these studies had interpretive problems^[10]=20 and have not been replicated.

[edit]=20 Color rendition

The issues with color faithfulness of some tube types are discussed=20 above.

[edit]=20 Dimming

Unless specifically designed and approved to accommodate dimming, = most=20 fluorescent light fixtures cannot be connected to a standard dimmer switch used for=20 incandescent lamps. Two effects are responsible for this: the waveshape = of the=20 voltage emitted by a standard phase-control dimmer interacts badly with = many=20 ballasts and it becomes difficult to sustain an arc in the fluorescent = tube at=20 low power levels. Many installations require 4-pin fluorescent lamps and = compatible controllers for successful fluorescent dimming; these systems = tend to=20 keep the cathodes of the fluorescent tube fully heated even as the arc = current=20 is reduced, promoting easy thermionic emission of electrons into the arc = stream.

[edit]=20 Disposal and recycling

The disposal of phosphor and particularly the mercury = in the=20 tubes is an environmental issue. (Incandescent lamps do not contain=20 mercury.)

For large commercial or industrial users of fluorescent lights, = recycling=20 services are available in many nations, and may be required by = regulation. In=20 some areas, recycling is also available to consumers. The need for a = recycling=20 infrastructure is an issue with instituting proposed bans of = incandescent=20 bulbs.

[edit]=20 Tube designations

The examples and perspective in this article or section may not=20 represent a worldwide=20 view of the subject.
Please improve this article or discuss the issue on = the talk=20 page.

Note: the information in this section might be inapplicable = outside of North=20 America.

Lamps are typically identified by a = code such as = F##T##,=20 where F is for fluorescent, the first number indicates the power in = watts (or=20 strangely, length in inches in very long = lamps), the T=20 indicates that the shape of the bulb is tubular, and the last = number is diameter in=20 eighths of an inch. Typical diameters are T12 (1=C2=BD" or 38 mm) for residential = bulbs=20 with old magnetic=20 ballasts, = T8 (1" or=20 25 mm) for commercial energy-saving lamps with electronic ballasts, and = T5=20 (⁵=E2=81=848" or = 16 mm) for very=20 small lamps which may even operate from a battery-powered device.

Slimline lamps operate on an instant=20 start ballast and are recognizable by their single-pin bases.

High-output=20 lamps are brighter and draw more electrical = current,=20 have different ends on the pins so they cannot be = used in the=20 wrong fixture,=20 and are labeled F##T12HO, or F##T12VHO for very high output. Since about = the=20 early to mid 1950s to today, General Electric developed and improved the = Power=20 Groove(R) lamp with the label F##PG17. These lamps are recognisable by = their=20 large diameter, grooved tubes.

U-shaped tubes are FB##T##, with the B meaning "bent". Most commonly, = these=20 have the same designations as linear tubes. Circular bulbs are FC##T#, = with the=20 diameter of the circle (not circumference or = watts)=20 being the first number, and the second number usually being 9 (29 mm) = for=20 standard fixtures.

Color is usually indicated by WW for warm white, EW for enhanced = (neutral)=20 white, CW for cool white (the most common), and DW for the bluish daylight white.=20 BL is used for blacklight lamps = commonly=20 used in bug=20 zappers. BLB is used for blacklight-blue lamps commonly used in = nightclubs.=20 Other non-standard designations apply for plant lights or grow=20 lights.

Philips uses=20 numeric color codes for the colors:

Low color rendition=20
- 33 the ubiquitous cool white (4000 K)=20
- 32 warm white (3000 K)=20
- 27 living room warm white (2700 K)

High color rendition=20
- 9xy "Graphica Pro" / "De Luxe Pro" (xy00 K; eg "965" =3D 6500 K) =
- 8xy (xy00 K; eg "865" =3D 6500 K)=20
- 840 cool white (4000 K)=20
- 830 warm white (3000 K)=20
- 827 warm white (2700 K)

Other=20
- 09 Sun tanning lamps=20
- 08 Blacklight=20
- 05 Hard UV (no phosphors used at all, using an envelope of fused=20 quartz)

Odd lengths are usually added after the color. One example is an=20 F25T12/CW/33, meaning 25 watts, 1.5" diameter, cool white, 33" or 84 cm = long.=20 Without the 33, it would be assumed that an F25T12 is the more-common = 30"=20 long.

Compact fluorescents do not have such a designation system.

[edit]=20 Other fluorescent lamps

Blacklights=20: Blacklights are a subset of fluorescent lamps that are used to = provide=20 long-wave ultraviolet = light (at=20 about 360nm wavelength). They are built in the same fashion as = conventional=20 fluorescent lamps but the glass tube is coated with a phosphor that = converts=20 the short-wave UV within the tube to long-wave UV rather than to = visible=20 light. They are used to provoke fluorescence = (to provide=20 dramatic effects using blacklight = paint and=20 to detect materials such as urine and certain dyes that would be = invisible in=20 visible light) as well as to attract insects to bug=20 zappers.

So-called blacklite = blue=20 lamps are also made from more expensive deep purple glass known as Wood's=20 glass rather than clear glass. The deep purple glass filters out = most of=20 the visible colors of light directly emitted by the mercury-vapor = discharge,=20 producing proportionally less visible light compared with UV light. = This=20 allows UV-induced fluorescence to be seen more easily (thereby = allowing=20 blacklight posters to seem much more dramatic). The blacklight = lamps=20 used in bug zappers do = not require=20 this refinement so it is usually omitted in the interest of cost; they = are=20 called simply blacklite (and = not=20 blacklite blue).

Sun=20 lamps=20: Sun lamps contain a different phosphor that emits more strongly in = medium-wave UV, provoking a tanning response = in most=20 human = skin. =

Grow=20 lamps=20: Grow lamps contain a phosphor blend that encourages photosynthesis = in=20 plants; they usually appear pinkish to human eyes.

Germicidal = lamps=20: Germicidal lamps contain no phosphor at all (technically making = them gas=20 discharge lamps rather than fluorescent) and their tubes are made of = fused=20 quartz that is transparent to the short-wave UV directly emitted = by the=20 mercury discharge. The UV emitted by these tubes will kill germs, = ionize oxygen = to ozone, = and cause eye=20 and skin damage. Besides their uses to kill germs and create ozone, = they are=20 sometimes used by geologists to = identify=20 certain species of minerals by the = color of their=20 fluorescence. When used in this fashion, they are fitted with filters = in the=20 same way as blacklight-blue lamps are; the filter passes the = short-wave UV and=20 blocks the visible light produced by the mercury discharge. They are = also used=20 in EPROM erasers.=20

Electr= odeless=20 induction lamps=20: Electrodeless induction lamps are fluorescent lamps without = internal=20 electrodes. They have been commercially available since 1990. A current is = induced into=20 the gas column using electroma= gnetic=20 induction. Because the electrodes are usually the life-limiting = element of=20 fluorescent lamps, such electrodeless lamps can have a very long = service life,=20 although they also have a higher purchase price.

Cold-= cathode=20 fluorescent lamps (CCFL)=20: Cold-cathode fluorescent lamps are used as backlighting = for LCD=20 displays in personal computer and TV monitors. They are also = popular with=20 case=20 modders in recent years.

[edit]=20 Science demonstrations

Fluorescent lamps can be illuminated by means other than a proper = electrical=20 connection. These other methods however result in very dim or very = short-lived=20 illumination, and so are seen mostly in science demonstrations. With the = exception of static electricity, these methods can be very dangerous if = done=20 improperly:

Static=20 Electricity=20
Van de = Graaff=20 generator=20
Microwaving=20
Tesla=20 coil=20
Capacitive=20 coupling with high-vo= ltage=20 power lines^[11]=20

[edit]=20 Film and video use

Special fluorescent lights are often used in film/video production. = The brand=20 name Kino Flos are used to create softer fill light and are less hot = than=20 traditional halogen light sources. These fluorescent lights are designed = with=20 special high-frequency ballasts to prevent video flickering and high=20 color-rendition index bulbs to approximate daylight color = temperatures.

[edit]=20 See also

[edit]=20 References

^=20 Page 183 of http://www.chem.unep.ch/MERCURY/Toolkit/UNEP-final-pilot-d= raft-toolkit-Dec05.pdf=20
^=20 http://lightingdesignlab.com/articles/mercury_in_fl/mercur= ycfl.htm=20
^=20 Floyd, et al. (2002), quoted on page 184 of Toolkit for identification and quantification of = mercury=20 releases (PDF)=20
^=20 Rihner M, McGrath H Jr (1992). = "Fluorescent=20 light photosensitivity in patients with systemic lupus erythematosus". = Arthritis Rheum 35 (8): 949=E2=80=9352. DOI:<= A=20 class=3D"external text" = title=3Dhttp://dx.doi.org/10.1002/art.1780350816=20 href=3D"http://dx.doi.org/10.1002/art.1780350816"=20 rel=3Dnofollow>10.1002/art.1780350816. PMID=20 1642660. =20
^=20 Beattie PE, Dawe RS, Ibbotson SH, = Ferguson J=20 (2003). "Characteristics and prognosis of idiopathic solar = urticaria: a=20 cohort of 87 cases". Arch Dermatol 139 (9): = 1149=E2=80=9354. PMID=20 12975156. =20
^=20 K=C3=BCller R, Laike T (1998). "The = impact of=20 flicker from fluorescent lighting on well-being, performance and = physiological=20 arousal". Ergonomics 41 (4): 433=E2=80=9347. =20
^=20 Veitch JA, McColl SL (1995). "Modulation of fluorescent light: flicker rate and light = source=20 effects on visual performance and visual comfort". Light Res = Tech=20 27 (4): 243=E2=80=93256. Retrieved on 2007-08-12. =20
^=20 Binnie CD, de Korte RA, Wisman T = (1979).=20 "Fluorescent lighting and epilepsy". Epilepsia 20 (6): = 725=E2=80=937. PMID=20 499117. =20
^=20 Colman RS, Frankel F, Ritvo E, = Freeman BJ=20 (1976). "The effects of fluorescent and incandescent illumination upon = repetitive behaviors in autistic children". J Autism Child = Schizophr=20 6 (2): 157=E2=80=9362. DOI:<= A=20 class=3D"external text" title=3Dhttp://dx.doi.org/10.1007/BF01538059=20 href=3D"http://dx.doi.org/10.1007/BF01538059"=20 rel=3Dnofollow>10.1007/BF01538059. PMID=20 989489. =20
^=20 Turner M (1999). "Annotation: = Repetitive=20 behaviour in autism: a review of psychological research". J Child = Psychol=20 Psychiatry 40 (6): 839=E2=80=9349. PMID=20 10509879. =20
^=20 http://www.richardbox.com/=20

[edit]=20 External links

Wikimedia Commons has media related to: =

Fluore= scent=20 lamp

NASA: The=20 Fluorescent Lamp: A plasma you can use=20
How Stuff Works: Are=20 fluorescent bulbs really more efficient than normal light bulbs?=20
How Stuff Works: How=20 Fluorescent Lamps Work=20
Sam's = F-Lamp=20 FAQ=20
The Fluorescent Lighting System=20
Washington Post: Energy Conservation Myths=20
The Lighting Design Lab: Should I Turn Off Fluorescent Lighting When Leaving = A=20 Room?=20
Energy=20 Star Lighting=20
Application notes for CCFL lamps.=20
History, Science and Technology of Light Sources: [6]=20
R. N. Thayer (1991-10-25). The = Fluorescent=20 Lamp: Early U. S. Development. The Report courtesy of General = Electric=20 Company. Retrieved on 2007-03-18.=20
Some = Better=20 Compact Fluorescent Lamps efficiency and quality details=20
[7] Dozens of raw visible spectra of fluorescent = and other=20 light bulbs.=20
Dimwits try to ban incandescent light bulbs - news = story from=20 Britain=20
Fluorescent Lighting, UK.D-I-Y Wiki=20
Fluorescent Tube Recycling=20
Information on Proper Disposal of Compact Fluorescent = Light Bulbs=20 (CFLs)=20
What to Do if=20 a Fluorescent Light Bulb Breaks=20
Fluorescent Tubes in the Workplace Article = explaining the=20 dangers of fluorescent tubes in the workplace

Lighting and Lam= ps=20 <= SPAN=20 title=3D"View this template">v =E2=80=A2 d =E2=80=A2 e
Incandescent:	Conventiona= l=20 - Halogen - = Parabolic=20 aluminized reflector (PAR)
Fluorescent:	Compact=20 fluorescent (CFL) - Linear = fluorescent=20 - Induction = lamp
Gas discharge:	High-= intensity=20 discharge (HID) - Mercury-vapor -=20 Metal-halide = -=20 Neon - Sodium=20 vapor
Electric arc:	Arc=20 lamp - HMI=20 - Xenon arc = - Yablochkov = candle
Combustion:	Acetylene/Carbide = -=20 Candle - Gas=20 lighting - Kerosene = lamp - Limelight - Oil lamp=20 - Safety lamp = - Petromax -=20 Rushlight
Other types:	Sulfur lamp = - Light-emitting= =20 diode (LED) - LED lamp (SSL) - Plasma - Electrolumi= nescent=20 wire - Chemiluminescence= =20 - Deuterium = arc=20 lamp - Radioluminescence=
Items used to manipulate resultant = light:	Mirrors - Prism = - Optical = fiber - Lens

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