The Royal Commission investigating the Pike River Mine disaster has heard the ventilation system at the mine limited the ability of men to escape following an explosion.
The hearings are now looking at the immediate cause of the first of a series of explosions that killed 29 men at the mine in November 2010.
The Royal Commission is now hearing from David Reece, an Australian expert who provided advice to the Department of Labour team which investigated the disaster.
Mr Reece said on Thursday that even after an explosion, getting the fan used to ventilate the mine back up and working is still the best means of ensuring the survival of the men underground.
He said this is the reason most fans in Australia are located above ground.
In the case of Pike River, the fan was underground, making it difficult to reach and repair in the case of an explosion.
Mr Reece said the single entry and exit point for the ventilation system at Pike was also unusual, and in Australia, would be considered acceptable only in the initial stages of a mine's development.
