Dogs and hi-tech equipment used to find people trapped in air pockets

The Strategy

Rescuers searching for survivors in the wreckage of the twin towers of the World Trade Centre will use a variety of technologies – though one of the most reliable is as old as man: sniffer dogs.

Experience in dealing with earthquakes, where buildings collapse but leave people alive in pockets of rubble, has led to the development of audio equipment that can detect the sound of human movements amid tons of rubble.

Rescuers will also have the use of cameras on fibreoptic cables that can be directed through the narrowest of gaps to locate people. Once they have been found, an inflatable bag that is capable of supporting several tons can be threaded down to create a passage to free them.

But although a handful of survivors have been pulled from the rubble, those on the scene expressed doubts yesterday that they will find many alive amid the carnage. "I lost count of all the dead people I saw," Rudy Weindler, a New York firefighter, told one reporter. "It is absolutely worse than you could imagine."

Some rescuers described the gruesome experience of finding body parts as they sifted through the thousands of tons of concrete and steel that was once part of New York's proud skyline.

Gary O'Shea, the assistant operations director of International Rescue – which more usually helps out in earthquakes and other natural disasters – said that while the best chance of recovering survivors was in the first 48 hours, it was "not definitive". He continued: "We've pulled people out five, seven, eight days after a major earthquake. There are people making phone calls from inside there. The problem is that they may be under tens of floors of debris. Even if people there are pessimistic, some people are clearly trapped in air pockets. As long as you've got air and some form of moisture, and there's no other major collapse, the chances of recovery are good."

He said people had been rescued up to 13 days after buildings collapsed, though he added that such events were rare.

International Rescue is on stand-by after offering its services to the United States government.

Six survivors – five firefighters and a policeman who had been trying to help the injured before the towers collapsed – had been hauled out of the wreckage by Wednesday morning, while rescue workers continued trying to detect signs of life. One person successfully called for help from his mobile phone.

The state-of-the-art technology on hand includes heat-sensitive cameras and sensors that can detect the carbon dioxide emitted when people breathe. There is also heavier hydraulic equipment such as "jaws of life" able to lift slabs of steel and concrete.

But the most effective in the short term may be the simplest: sniffer dogs that are trained to seek out people.

They are more agile than their human trainers, and more sensitive at finding people. "They are unbeatable at this," said one rescuer.