TRITIUM as exit signs, their application

Application of radiation- consumer product, safety and security.

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Exit signs use nickel cadmium (NiCad) emergency light batteries that are smaller than the lead acid batteries within emergency lights. Perhaps the easiest sign to mount is the self-luminous exit sign, which is powered by tritium.  

 A. type(s) of radiation/radioactive sources used

Tritium emits a beta electron which cannot even penetrate a piece of paper. Tritium is a low energy beta emitter, it is not dangerous externally(its beta particle are unable to penetrate the skin0, but it can be radiation hazard when inhaled, ingested via food and water, or absorbed through the skin.

Tritium is a naturally occuring radioactive form of hydrogen that is produced in the atmosphere when cosmic rays collide with air molecules. As a result, tritium is found in very small or trace amounts in groundwater throughout the world.

 B. General principles (theoretical description)

Power free exit signs require no electricity (AC) or battery power to work. They are illuminated via either photoluminescence ("glow-in-the-dark") or radioluminescence (low level nuclear decay). Since no AC hookup is required, installation is incredibly simple and does not require access to conduit, outlet, or the services of an electrician which translates to minimal installation costs. Since no power is required, there is zero lifetime power consumption cost! With no electronics or batteries, these signs also enjoy zero lifetime mainenance costs!

Self luminous tritium exit signs are illuminated via the radioluminescence of the phosphor coating of a glass tube by electrons emitted from a tritium gas. Basically the electrons of the phosphor coating are excites into emitting electromagnetic radiation in the visible spectrum (I.e. light). this illumination is internal, without the need for a source of electrical power, therefore these tritium exit signs are also known as ‘self luminous exit signs’ or ‘self luminous tritium exit signs’

The process is very similar to that in your television set picture tube where an electron is used to illuminate the front screen of the tube. The electron from tritium however has only about1/4 of the energy of the electron in color tv picture tube. That is why self-luminous exit signs are not visible in daylight while TV picture are. The electron from the tritium gas has such low energy that it cannot even penetrate an ordinary sheet of paper, and so actually never escapes the sealed glass tube.

 C. Benefits and limitations

Tritium exit signs are a self luminous exit sign model that is able to produce emergency illumination without the use of electricity. Tritium exit signs save money on installation costs as well as operation costs, by requiring no wiring to be ran to the sign (thus no electrician to be hired for installation) as well as no addictions to the electricity bill.

Ø Use no electricity

Ø Last for up to 25 years

Ø Do not require wiring during installation

Tritium exit signs use a gas within the fixture to power the bulb itself via radioactive combustion. Tritium exit signs operate much like a fluorescent light fixture would- except no electricity is required for the “spark” to initially produce illumination within the fixture.

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