Germicidal lamp

A germicidal lamp is a special type of lamp which produces ultraviolet light (UVC). This short-wave ultraviolet light ionizes oxygen to produce ozone and can kill many surface pathogens.

There are two common types available:

* Low pressure lamps
* Medium pressure lamps

Low pressure lamps

Low-pressure lamps are very similar to a fluorescent lamp, with a wavelength of 253.7 nm.

The most common form of germicidal lamp looks similar to an ordinary fluorescent lamp but the tube contains no fluorescent phosphor. In addition, rather than being made of ordinary borosilicate glass, the tube is made of fused quartz. These two changes combine to allow the 253.7 nm ultraviolet light produced by the mercury arc to pass out of the lamp unmodified (whereas, in common fluorescent lamps, it causes the phosphor to fluoresce, producing visible light). Germicidal lamps still produce a small amount of visible light due to other mercury radiation bands.

An older design looks like an incandescent lamp but with the envelope containing a few droplets of mercury. In this design, the incandescent filament heats the mercury, producing a vapor which eventually allows an arc to be struck, short circuiting the incandescent filament.

Medium pressure lamps

Medium-pressure lamps are much more similar to HID lamps than fluorescent lamps.

These lamps radiate a broad-band UV-C radiation, rather than a single line. They are widely used in industrial water treatment, because they are very intense radiation sources. They are as efficient as low-pressure lamps. Medium-pressure lamps produces very bright bluish white light.

Auxiliary equipment

As with all gas discharge lamps, all of the styles of germicidal lamps exhibit negative resistance and require the use of an external ballast to regulate the current flow through them. The older lamps that resembled an incandescent lamp were often operated in series with an ordinary 40 W incandescent "appliance" lamp; the incandescent lamp acted as the ballast for the germicidal lamp.

Uses

Germicidal lamps are used to sterilize workspaces and tools used in biology laboratories and medical facilities. They are also used wherever ozone is desired, for example, in the sanitizing systems of hot tubs and aquariums. They are also used by geologists to provoke fluorescence in mineral samples, aiding in their identification. In this application, the light produced by the lamp is usually filtered to remove as much visible light as possible, leaving just the UV light.

The light produced by germicidal lamps is also used to erase EPROMs; the ultraviolet photons are sufficiently energetic to allow the electrons trapped on the transistors' floating gates to tunnel through the gate insulation, eventually removing the stored charge that represents binary ones and zeroes.

Germicidal lamps are also used in waste water treatment in order to kill microorganisms.

LINKS

* [http://www.bio-uv.com Water disinfection by ultraviolet rays] Low pressure lamps and medium pressure.

Safety concerns

Short-wave UV light is harmful to humans. In addition to causing sunburn and (over time) skin cancer, this light can produce extremely painful inflammation of the cornea of the eye, which may lead to temporary or permanent vision impairment. It can also damage the retina of the eye. For this reason, the light produced by a germicidal lamp must be carefully shielded against both direct viewing and reflections and dispersed light that might be viewed.


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • germicidal lamp — a type of mercury arc lamp whose radiation kills bacteria …   Medical dictionary

  • Ultraviolet germicidal irradiation — (UVGI) is a sterilization method that uses ultraviolet (UV) light at sufficiently short wavelength to break down micro organisms. [National Institute for Occupational Safety and Health. (2008, April). NIOSH eNews, 5(12). Retrieved September 10,… …   Wikipedia

  • Fluorescent lamp — A fluorescent lamp or fluorescent tube is a gas discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light.Unlike… …   Wikipedia

  • Gas-discharge lamp — See also: Gas filled tube Germicidal lamps are simple low pressure mercury vapor discharges in a fused quartz envelope. Gas discharge lamps are a family of artificial light sources that generate light by sending an electrical discharge through an …   Wikipedia

  • Oil lamp — Neolithic stone lamps in Thousand Lamp Museum in Qiandeng town of Kunshan …   Wikipedia

  • Compact fluorescent lamp — Low energy light bulb redirects here. For other low energy bulbs, see LED lamp. The tubular type compact fluorescent lamp is one of the most popular types in Europe …   Wikipedia

  • Tanning lamp — Tanning lamps (sometimes called tanning bulbs in the United States or tanning tubes in Europe) are the part of a tanning bed, booth or other tanning device which produces ultraviolet light responsible for tanning. While there are literally… …   Wikipedia

  • Metal-halide lamp — A metal halide gas discharge lighting system provides illumination for a college baseball game at Olsen Field in College Station, Texas, United States. Note the various colors of the lights as they warm up. Metal halide lamps, a member of the… …   Wikipedia

  • Mercury-vapor lamp — Mercury Lamp redirects here. For the character in the Rozen Maiden anime and manga, see Characters of Rozen Maiden. A 175 watt mercury vapor yard light approximately 15 seconds after starting …   Wikipedia

  • Sulfur lamp — The sulfur lamp (also sulphur lamp) is a highly efficient full spectrum electrodeless lighting system whose light is generated by sulfur plasma that has been excited by microwave radiation. The technology was developed in the early 1990s, but,… …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.