GREYMOUTH // The 29 workers trapped after a coal-mine disaster in New Zealand could have survived by sealing themselves off from toxic gases, experts said today, but they warned that rescuers must hurry to get them out.
New Zealand's prime minister, John Key, said there was "every chance" the men could be alive, having been trapped in the Pike River coal mine since Friday, but as families waited anxiously the mood at the site was grim.
Queensland University's David Cliff, who has worked in mine safety for almost 20 years, said the men could be sitting in an air pocket but it would be a race against time to bring them to the surface.
"The general rule with a coal mine is the faster the better," he told AFP, warning about the build-up of poisonous gases. "You have got to get out of there in a hurry."
Efforts to reach the miners have been thwarted by high levels of methane and carbon monoxide, and fears of a second blast, preventing frustrated rescuers from entering the shaft.
Mr Cliff said: "If they were in a refuge of some sort, if they have a supply of air, they might last a long time - we should not give up on that sort of hope.
"If they have been lucky and they are in the area of the mine which is relatively unaffected by the explosion, then they could have barricaded themselves in."
This would involve putting a cloth or other material up to isolate the area from the harmful gases. Another possibility was that the men had grouped at an outlet for the compressed air pipes which run through the mine.
But Mr Cliff said in stark contrast to the miraculous recovery of 33 miners trapped for almost 10 weeks in a mine in Chile, there is no guarantee than those at Pike River have access to breathable air, since the mine's ventilation system had stopped and methane was seeping out of the coal.
The mine, dug into a hillside, is accessed by a horizontal, 2.5-kilometre tunnel, while a large ventilation shaft brings fresh air from the surface about 150 metres above.
Pike River's chief executive, Peter Whittall, would not speculate on what conditions the men could be surviving in, but said air would be the priority.
"It would certainly be quite hot and stuffy because there's not a lot of ventilation down there," he told reporters.
Each man would have been carrying a breathing device which could generate oxygen for 20 to 60 minutes, and there were some of these stored underground.
But Daniel Rockhouse, 24, who survived the blast and stumbled to the surface in an agonising two-hour trek, has told of dragging an unconscious fellow miner to a "fresh air station" only to find it was flooded with poison gas because its door had been left open, while its only phone was not working.
"I said, 'you've got to be bloody kidding me!' I screamed and kicked the wooden seats," Mr Rockhouse said, He revived the man with compressed air and then helped him out of the smoke-filled mine shaft.
A Wellington-based mining consultant, Dave Feickert, said it was obvious the two survivors were extremely lucky. He said people needed to remain hopeful but warned that "the history of these things is usually pretty grim".
Ron Land, chairman of Coal Services Australia, which has sent 10 technical experts to Pike River to help the rescue, agreed hopes were fading.
"The length of time now, it's 72 hours since the incident, you are always hopeful but with the passing of each hour the chances of survivors is lessening," he told AFP.
But Professor Bruce Hebblewhite, head of engineering at the University of New South Wales in Sydney, said there were too many unknowns to dismiss their survival chances.
He said a major concern was whether a coal fire was still burning underground, creating poisonous fumes and risking setting off another blast.
One option could be waiting for the fire to burn itself out, he said.
"It could be a long time - you can't put a handle on it. It could be a major ongoing problem," Professor Hebblewhite said.
Mr Cliff said in the past, mine blasts have been followed by another explosion, for example at Australia's Moura No 2 coal mine in 1994, when a secondary blast sealed the fate of 11 trapped miners.
"There was an explosion on the Sunday night, and then 36 hours later just before rescue teams were getting ready to go in, there was a second explosion," he said.