Gas buildup may be to blame - experts

Smoke billows from a ventilation shaft at the Pike River Coal mine. Photo / Greymouth Star

Concerns are growing that a buildup of methane gas, caused by faulty ventilation systems, may have been the cause of the explosion in Pike River Mine.

Peter Griffin, from the Science Media Centre, wrote in his latest blog entry that if the ventilation systems were not properly functioning, there might have been a buildup of the dangerous gas. This scenario is also known as firedamp.

"Ventilation shafts are common features of underground mines and Pike River was employing ventilation as a safety measure at its mine," Griffin wrote.

"However, it is a tricky business estimating and managing methane levels in mine shafts, as faults in rock can become conduits for methane from other geographically removed sources."

Mining regulations require methane to be diluted in the ventilation air, and then vented to the atmosphere.

John St George, a lecturer in the department of civil and environmental Engineering at the University of Auckland, said detection systems were designed to sound an alarm when methane levels reach a certain level.

"That's when everyone gets out of the mine," said Dr St George.

It is not known if detection systems were in working order at the time of the explosion.

All equipment used in mining is specially designed to reduce the chance of a spark which could cause an explosion.

Miners are not allowed to take electronic devices such as iPods and mobile phones into the mine as they might cause a spark to set off an explosion.

"One hopes they are in a safe place with oxygen," said Dr St George.

Another possible source of the explosion is a buildup of coal dust.

"This hazard is as old as mining itself," said Griffin.

"Working at coal seams with industrial equipment throws up a large amount of dust, which if not properly extracted or appropriately dispersed can explode."

Methane

* An odourless gas that is released when coal is mined.

* Can combust if it collects in concentrated pockets.

* Ventilation systems remove methane from the mine and disperse it into the atmosphere.

* Devices on equipment and on miners detect if methane reaches dangerous levels.