Many premises require exit signs at the egress and along the pathway to guide the people out of the premises. Even under the state laws it is mandatory to have the exit signs at all important locations along the pathway so that in case of emergency the premises could be easily vacated. There are many models of exit signs available that are operable through various means.
Some exit signs run on electricity and some on either batteries or are self luminous. The battery operated exit sign is not preferred in its present state. This is because, though it saves one on installation cost, the maintenance cost is very high, as one has to replace the batteries frequently.
The installation cost is negligible as there is no need for wiring and hence the electrician. But this type of exit sign has other disadvantages too in the sense that this sign cannot be installed at high levels or in inaccessible areas. They have to be installed only in those areas that are easily accessible for the replacement of the battery.
If one is not very particular, one can go in for the electrical LED exit signs that have battery backup. In this variety of exit signs, the battery is constantly charged by the electrical power and when there is power outage, can glow and illuminate for approximately 90 minutes. There is a better substitute to the battery operated exit sign in the form of the self luminous exit signs.
These signs are available as photo luminescent and self-luminescent. Out of these the self luminescent is the more popular exit sign as it has many advantages over the rest. It has a long life-span that ranges from 10 to 20 years; is completely maintenance-free for its entire life and most importantly does not work on power supply.
The self luminescent exit sign illuminates on its own for 24 hours a day and for its entire lifespan. This is because of Tritium, a radioactive substance that is certainly found in the upper atmospheric levels due to the reaction with the cosmic rays. It is also produced commercially in the reactors that are producing electricity as byproduct. Tritium is radioactive isotope of the hydrogen molecule and has a half-life of 12 ½ years. This makes it as having one of the shortest lives amongst the known radionuclide.
The Tritium gas is filled in the phosphor coated glass tubes where its electrons interact with the phosphor to produce illumination. As the energy released is so low that it cannot even pass through ordinary sheet of paper, it has been termed safe by the USNRC. The main advantages of these exit signs are that they not only save you the installation cost, they also save you on the electricity bills and other maintenance related costs.
These exit signs can also be easily installed without the help of electrician, as they do not necessitate any sort of wiring. One just has to mount it at the desired location and at multiple places even the inaccessible areas. It is similarly beneficial for those who have to put up temporary structures and then dismantle it and relocate as these signs can be easily dismantled and transported to the other site for reinstallation.