A Mines Rescue Service report on the Pike River mine found that its alternative means of escape, a 108 metre ventilation shaft, would have been "extremely difficult" to use in an emergency and identified this as a "major concern" as it was “virtually impossible” to climb the vent shaft ladder during a fire.

Whittall told the inquiry he could not recall whether the mine’s personnel ever had a trial evacuation using the ventilation shaft.

The company had not gone ahead with constructing another 10-metre to 15m passage as outlined in its original 2005 plan, as it struggled with cost overruns, from $NZ207million to about $350 million.

"Current senior management has not been able to deliver the Pike River Coal project on schedule or budget," a report by independent mining consultancy BDA said in May last year.

Whittall agreed with a statement by counsel assisting the commission Simon Mount that Pike River had forecast an increase in working capital shortfall from between $6 million and $12 million to between $20 million and $24 million.

Whittall staunchly defended the mine’s gas monitoring system, which has been the focus of criticism for not alerting personnel about rising methane levels in the mine.

He told the inquiry independent laboratory tests had indicated that the mine’s coal was not prone to spontaneous combustion and that gas monitors installed throughout the mine could accurately measure levels of methane, oxygen and carbon monoxide.

“Tests undertaken by an independent laboratory showed that the mine’s coal had a lower inherent propensity to spontaneously combust, meaning the coal itself had a low likelihood of self heating in normal atmospheric conditions,” he said.

“Two different methods of gas monitoring were planned for the mine: real time monitoring and tube bundling.

“Real time monitoring measures and transfers data immediately to the control room.

“Real time monitoring is used to measure data such as carbon monoxide and methane levels and provides information in order to generate a quick response.

“The real time system is used to measure a discrete number of points where immediacy of information is important such as electrical installations or main fans.

“This system was in place and functioning at the mine.”

Whittall said the mine also had an active gas management program.

“The company had an active programme of inseam directional drilling with inseam boreholes radiating out over 600 metres in length,” he said.

“The borehole information was used for seam definition and mine planning. During drilling, gas was drawn away from the hole’s collar using a stuffing box to capture the gas and direct it into a gas drainage line.

“Following completion of the hole, the remnant boreholes were attached to methane drainage lines. This assisted the drainage of gas from the coal, ahead of mining operations.

“The gas was either vented to the surface via a gas riser borehole, or free vented into the mine’s return ventilation to be diluted and exhausted from the mine using the main ventilation system.”

The predominant gas in the Brunner coal seam is methane. Generally, the seam is quite gas permeable and therefore gas within the seam, which ranges from negligible in the east to approximately eight cubic metres per tonne in the west flows quite freely from cut coal and roadways, Whittall said.

Whittall resumes his testimony this morning.