Survivors of the Whakaari White Island disaster will give accounts of how the tragedy forever changed their lives, when the sentencing of companies guilty of safety failings starts today.

Six parties will be sentenced in the two-week hearing held in Auckland at the Environment Court, following a criminal trial into the 2019 disaster which killed 22 people and injured 25 others.

After an extensive investigation, WorkSafe charged 13 parties for safety failings that put tourists and workers at undue risk - six had their charges dismissed, another six pleaded guilty, one of which has been sentenced.

Whakaari Management, the company that granted access to the volcanic island, was found guilty at the trial and is among those being sentenced.

The court will consider what reparation is available to survivors, but at a previous hearing, Judge Evangelos Thomas said there will not be enough money to properly compensate them.

"We would love to properly recompense everyone who has suffered, but there's only going to be a finite amount of funds available and, as is always the case, it's going to be wholly insufficient to properly compensate even those who are the primary victims," he said.

"It's an awful position for us all to be in, to be even having this discussion but ... it's not for lack of acknowledging what everybody's gone through. It's just the legal reality of how we divide up what, in the scheme of things, is going to be a very small pot."

The companies being sentenced face fines up to $1.5 million but if the party being sentenced cannot afford both the fine and compensation, the judge will order reparation only.

Alongside Whakaari Management which was found guilty, the companies that pleaded guilty and are due to be sentenced are White Island Tours on two charges, the three helicopter companies Volcanic Air, Aerius and Kahu each on two charges, and GNS on one charge.

Judge Thomas said GNS, the crown research institute that monitors volcanoes, will be sentenced separately on Thursday because "the issues relating to GNS are discrete and separate from those relating to other defendants".

GNS faces a fine of up to $500,000 for failing to consult with contractor helicopter pilots about the risks of flying its scientists to the volcanic island for field trips.

Meanwhile, the owners of Whakaari have asked the courts to award them costs, following the dismissal of charges against them.

Last September, Andrew, James, and Peter Buttle had their individual charges from WorkSafe dismissed.

Their company, Whakaari Management, was later convicted on one charge for health and safety failings in the lead-up to the fatal eruption.

Judge Thomas, from the Auckland District Court, deferred hearing the costs application.

He said there were active appeals from companies that were also charged by WorkSafe, and these could impact potential cost liability.

-Amy Williams/RNZ.