Mine's underground fan raises questions

Photo / Supplied

Of nine fatal coal mine explosions since 1879, Pike River is the first where rescuers failed to recover any bodies within 24 hours.

Local mining researcher Peter Ewen points to Pike River being the only mine where the main ventilation fan was underground, a compromise that might have limited rescue options for the sake of ecology and efficiency.

"Some questions have got to be asked about the fan," Mr Ewen said.

"The fan was 100m underground, and once the explosion happened, there was no way they were going to restore ventilation because they couldn't get to it."

If the ventilation was at the top of a hill, as at other mines, rescuers could walk to it, start it up, and get the air back inside, he said.

"Who went against the old way of doing it by allowing the fan in the mine itself? You had no access to it once there was an explosion."

The environmental disruption that could be caused by putting the fan at the top of the shaft had been one consideration.

Mine engineering expert David Bell said most mines had their main fans at the top of ventilation shafts.

"I suspect one of the reasons you would have it at the bottom is you would try to get as much pull as you could. It would be more efficient to have it at the bottom of the shaft," Mr Bell said.

Pike River did not return calls made by the Weekend Herald about the mine's ventilation this week, but during the rescue operation, officials repeatedly said they were reluctant to do anything that would change the atmosphere inside.

They had brought up a fan to the mine entrance but never switched it on because of this concern.

Other safety concerns have been raised by Pike River miners, including former employee Brent Forrester and in text messages sent by killed miner Conrad Adams to friends earlier this year.

Mr Adams complained of frequently smelling hydrogen sulphide inside the mine - a gas Mr Bell said was more toxic than carbon monoxide and even cyanide gas.

Mr Forrester told the Timaru Herald that gas sensors at Pike River were not always calibrated.

He recalled an incident where a miner sprayed fresh air on his sensor to stop it from warning that gas levels were too high.