Rockhouse resumed giving evidence yesterday at phase two of the inquiry on the Pike River mine disaster that killed his youngest son and 28 other men.

Under cross-examination Rockhouse admitted that an explosion at the mine had never crossed his mind.

"I didn't expect the mine to blow up," he said.

Lawyer Nigel Hampton noted this thinking was a “repeated theme” in the inquiry.

“We heard it from Mr White yesterday or the day before, that nobody expected this mine to blow up and therefore you didn’t plan for that occurrence,” Hampton said.

Rockhouse confirmed that an explosion was not considered as a prospect in safety planning.

“Well we went through the risk assessment process and we had about five different scenarios in respirable and irrespirable atmosphere and I think that we were more looking at it from an irrespirable atmosphere as a consequence of a machine catching fire [as] opposed to an explosion,” Rockhouse said.

In his earlier testimony Rockhouse said he didn’t like the idea of using the ventilation shaft, known as Alimak Rise, as a long term emergency egress.

Rockhouse confirmed his views when he told the commission a risk assessment report into the Alimak found the raise was not suitable as a second means of egress from the mine.

“The report was sent out for comment but still required Mr Whittall’s approval and sign-off and he failed to do that,” Rockhouse said.

Rockhouse admitted a second tunnel would have been a better safety alternative to the ventilation shaft which was put in place as an egress.

Rockhouse also informed the inquiry of senior management’s decision to reject a $300,000 emergency chamber, although he had viewed it as essential.

“Eventually Mr Whittall declined the proposal … I was informed that he believed that using the Alimak raise … would suffice as a second means of egress from the mine,” Rockhouse said.

“It was at about this time that Mr Whittall[’s] and my personal relationship began to deteriorate.”

When asked if the emergency response plan on the day of the explosion was sufficient, Rockhouse said it was a good plan but conceded more regular training and scenario-based training could have improved the efficiency of the plan.

The commission was told by Rockhouse that he was understaffed, and his pleas for assistance were dismissed.

"I needed more people to start doing the physical auditing. There weren't enough people on the ground to do the auditing,” he said.

"On the one hand I was expected to produce world class systems, but they didn't understand that the other side of that equation was people on the ground to maintain the systems.

"I was understaffed and couldn't achieve that without additional help.”

Rockhouse spent the earlier part of his testimony retracing his steps on the day of the explosion last November, and the moment he realised his son was in the mine.

“I sat in stunned silence as I realised the seriousness of my son Ben still being underground,” he said.

Rockhouse said he thought his son was at home because his shift finished at 3pm, and was not aware that his son had returned to the mine.