Green gas makes its bid as clean fire fighter: An ozone-friendly agent could fill Halon's role in computer room fires. Roger Trapp reports

THE SEARCH for a replacement for Halon, the most effective protection against fire in computer rooms, has concentrated on creating another gas that will interfere with the chemical reaction of the fire. But Wormald International, part of what is perhaps the world's largest fire-protection group, claims to have found the answer by taking a different approach.

As reported here on 7 March, it has been found that the Halon gas is hazardous to the ozone layer. Under an international protocol, production will cease on 1 January 1994.

Although supplies will continue to be available for some time after the main manufacturers, Du Pont and Atochem of the US, halt production, they will be in diminishing amounts and at higher prices. This crisis has sparked the formation of the Halon Users National Consortium, with the support of the Department of the Environment, to explore ways of managing existing banks of Halon and to study options for the future.

Halon replacements have foundered so far because even though not harmful to the ozone layer, they contribute to global warming.

Wormald's product, Inergen, is a natural substance that is 52 per cent nitrogen, 40 per cent argon and 8 per cent carbon dioxide. As a result, said David England, the company's general manager for marketing and strategy, it was particularly suited to Germany and Scandinavian countries, where strict environmental policies have created an effective ban on synthetic materials.

Inergen - which has been introduced at about 150 sites around Europe, 30 of those in the UK - also differs from Halon in the way it deals with a fire. Rather than being involved in the chemical reaction, it depletes the oxygen level. But the carbon dioxide helps to stimulate the breathing of fire- fighters. It was developed through research in the US, where Wormald's parent company, Tyco Laboratories, is based. The study was aimed at finding methods of fighting fires in submarines and spacecraft, where air is in short supply. In fact, Mr England said, the technology had been available since the Second World War; it had simply not been needed until environmental concerns about alternatives arose.

However, Ken Simpson, project manager of the Halon users' group, said Inergen was just one of a number of products claiming to be the sought- after substitute for Halon. Some used gases, others chemicals, and still others were based on water.

The special qualities of the substance being sought make it unlikely that there will ever be a true 'drop-in' replacement for Halon, but the search will go on because the stakes are so high. For example, the world's airlines, which employ Halon in their systems to extinguish cabin fires, want to be able to use the hoses and nozzles they already have because the cost of changing them all would be huge.

(Photograph omitted)