Pike River: Gagging mine more efficient

Peter Whittall. Photo / Mark Mitchell

The "gagging" of the Pike River mine would be "several hundred times quicker" than other methods being considered to stabilise the air underground, says the company's chief executive.

Peter Whittall re-iterated that the air in the mine was volatile and that a recovery operation would not go ahead until authorities were certain conditions were safe.

Only then would Mines Rescue staff be allowed to enter the tunnel network.

While specialists are still "assessing and evaluating" the best to way to stabilise the mine, Mr Whittall said his preferred option was "gagging the mine" as he believed this would get the men out from underground sooner.

"The quickest option is the gag engine. It's some several hundred times quicker than the other options. That's my preferred option, to get this done as quickly as possible," he said.

"The gag engine was delivered to the Hokitika airport form Queensland and that was flown in overnight, that's now been rebuilt and trucked up the mine site."

While it would still take days to set up the equipment to gag the mine, the process itself would be relatively quick, he said.

"The actual pumping through of inert gases will take hours, not weeks. It's quite a quick job for a small mine."

"Gagging" a mine involves displacing the air underground with nitrogen and carbon dioxide to remove any oxygen present.

As combustion cannot occur without the presence of oxygen, this process puts out any fires still alight and removes the risk of another explosion.

Mr Whittall did warn that the first effort to flush oxygen out of the mine may fail and it could take numerous attempts before it was successful.