The man charged with overseeing the Pike River mine smelled diesel or exhaust in the air after it was hit with an explosion that killed 29 men.

Chief Coroner Neil MacLean opened the coronial inquest into the Pike River mine disaster just after 10am, at the District Court in Greymouth.

A statement from Pike River manager Douglas White was read to the inquest this afternoon.

It said Mr White went outside after being told by Daniel Duggan that power had gone out in the mine at 3.50pm.

He decided to drive to the mine portal to check communications after smelling "excessive diesel or exhaust fumes" in the air outside the mine administration building carpark, his statement said.

Everything seemed normal at the portal, with ventilation working and no unusual smell in the air, it said.

Mr White said it was only when an electrician sent in to restore power in the mine found the stalled juggernaut and the sprawled body of survivor Daniel Rockhouse that the explosion was detected.

His statement said he contacted emergency services and Pike River Coal headquarters in Wellington after being told of the explosion.

He then boarded a helicopter that took him to the mine's ventilation shaft at 5.02pm, where he saw "light or wispy smoke" coming out of the shaft and damage to the area around it.

His statement said among his first tasks on returning to the mine base was making sure a tag board which kept track of which men were still in the mine remained untouched.

Because of that he can be sure the 29 lost miners were underground at the time of the explosion, it said.

"These people were underground at the time of the explosion and remain underground."

'Chance of survival nil'

Superintendent Gary Knowles earlier told the inquiry today that expert evidence from Dr Robin Griffiths of the University of Otago showed the first blast on November 19 would have released a lethal combination of carbon monoxide and carbon dioxide.

All 29 miners would have died within five minutes, the inquiry heard.

"The chances they would have lived would have been nil.

"In the presence of such low oxygen hypoxic hypoxia would have occurred rapidly.

"They would have remained unconscious until death three to five minutes later."

Mr Knowles read out a list of all the miners and the last time they were seen before they died.

Many of the miners were last seen by family on November 19 - the morning of the explosion.

Tale of heroism

Mr Knowles told the court one of the men in the mine, Daniel Rockhouse was working about halfway into the mine when the blast happened.

Mr Rockhouse saw a "white flash", was blown off his feet, and was deafened by the noise.

The mine filled with smoke, Mr Knowles said.

He was able to put a gas mask on, but panicked and fell unconscious for about 20 minutes.

When Mr Rockhouse awoke he was able to get to an oxygen valve and also rang the mine base to alert them to the explosion.

"He made his way back out of the mine where he came across another miner, Russell Smith," Mr Knowles said.

Mr Smith was semi-conscious but unable to put a gas mask on, so Mr Rockhouse picked him up and dragged him further back down the mine shaft.

When Mr Smith was recovered enough he was able to walk by himself.

The pair kept stopping on their way back to check for light and any sign of life, but none could be seen, Mr Knowles said.

Purpose of inquest

A spokesman for Judge MacLean yesterday said the inquest would be limited to establishing the time and cause of the men's deaths, and formally confirming their identities to allow death certificates to be issued.

Wider issues concerning the cause and possible prevention of the mine tragedy would be covered later by a Royal Commission of Inquiry.

The coroner is expected to hear evidence from four expert witnesses, as well as police and Pike River Coal representatives.

"Their evidence will help him determine as far as possible the time and manner of death, and if he can do that, that will allow the issuing of death certificates," the spokesman said.

The coroner anticipated making an oral finding on the time and cause of death at the end of proceedings. He would then adjourn the inquest indefinitely so as not to prejudice the Royal Commission.

However, Judge MacLean could re-open the inquest later if necessary.

"He will...let the Royal Commission take its course and then if he feels any need to re-open his inquest, he will. Otherwise he will just close it," the spokesman said.

The hearing is set down today, and tomorrow if required.