Review sought over 'radioactive' signs

PUBLISHED : Sunday, 25 May, 2008, 12:00am
UPDATED : Sunday, 25 May, 2008, 12:00am

The government has failed to see the light when it comes to allowing the installation of glow-in-the-dark safety signs that use radioactive tritium, according to an application for a judicial review.

Popular Signs, the sole Hong Kong distributor of 'self-luminous' gaseous-tritium light devices made by the US-based Isolite Corporation, lodged the application in the High Court on Friday.

It asks the court to quash a decision by the Radiation Board not to allow exemptions from licensing requirements for buildings using two or more of the devices.

Tritium is a radioactive element that is also used in the production of nuclear weapons, luminous watch dials and night-vision equipment.

The board, said Popular Signs, had set a maximum radiation content for buildings that was too low. As a result, companies wishing to install the devices needed to spend extra time and money obtaining licences that needed to be renewed each year.

The signs consist of a glass tube coated on the inside with a luminous material that creates light when exposed to the radiation emitted by decaying tritium atoms.

Because they are powered by radiation, they do not need an external power supply and will continue to work once all other light sources have been extinguished.

The company cited a 2001 report prepared for the Electrical and Mechanical Services Department that found there were about 2 million exit and direction signs in Hong Kong that consumed more than 1 per cent of the city's electricity production.

It also presented evidence to suggest that even if a sign were destroyed and someone breathed in all the tritium gas, the exposure would not be life-threatening. In fact, it would be 'of the order of the annual radiation dose limit. Such a release does not represent a danger to life.'

Otherwise, the company said, the devices gave off no radioactivity because the thickness of the glass was such that it stopped any emissions.

The company claims the board is misinformed and the court should step in to quash the decision.