Unite Union is calling for an investigation into whether "tens of thousands" of workers had their health endangered by the fire at the SkyCity Convention Centre last week.

It is also urging its members to lodge ACC claims if they were affected by smoke inhalation.

Unite Union organiser Joe Carolan said about 1000 people worked in the buildings adjacent to the fire and there were 450 delegates at a conference.

​Carolan said when he got to the building on the Tuesday that the fire broke out, "heavy, acrid smoke" had engulfed the floors.

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JASON DORDAY/STUFF Unite Union is calling for an investigation into whether "tens of thousands" of workers had their health endangered by the fire at the SkyCity Convention Centre.

"The alarm was raised about 1:47, and I got up there 20 minutes later," Carolan said. "On the sixth floor, it stunk of smoke. I got up to the gaming floor, and I couldn't believe it, people were still spinning the roulette wheel."

Carolan said smoke also came through the balcony on Hobson St and the convention centre's car park.

"The SkyCity International Convention Centre burned for days and, particularly on Tuesday afternoon and all day Wednesday, huge amounts of toxic smoke were released into the central city. This is by far the most densely populated area in New Zealand, with well over 100,000 people working there daily, yet many central city workplaces kept their employees working throughout or only closed after hours of exposure."

The union wanted to know what WorkSafe NZ did, and what it was going to do, to protect workers' health and safety.

"We have made numerous attempts over the last week to report our concerns and get them investigating, without any meaningful response. Despite promises to respond by close of business yesterday to our numerous requests for investigations we have still not heard back."

SUPPLIED The union's urging its members to lodge ACC claims if they were affected by smoke inhalation.

The union said there should be an investigation to determine whether businesses failed to get workers out of harm's way.

Firefighters said chemicals from the blaze were likely to include cancer-causing carcinogens.

Wattie Watson, national secretary of the New Zealand Professional Firefighters' Union, said: "You can see it is toxic because of the blackness of the smoke. There can be 70,000 carcinogens in building products. We know through a huge amount of research that repeated exposure has caused high levels of certain cancers in firefighters.

"People will have been exposed, but hopefully, that is their only exposure to something like that. Firefighters deal with it with every other fire."

ABIGAIL DOUGHERTY/STUFF Unite says about 1000 people work in the buildings around the fire.

Health and safety lawyer Brett Harris said the fire was an "unprecedented", "timely wake-up call" for employers.

He said most businesses took an appropriate level of caution: "Faced with the uncertainty about the content and true risk of the smoke across central Auckland, anecdotally, most businesses, government agencies, and building owners appear to have acted responsibly and proportionately.

"That said, it is a timely reminder of what the law expects; to protect workers' health, as well as safety, and to provide a healthy work environment, monitoring exposure to substances, especially routine exposures, as much as practically possible."

A spokesperson for WorkSafe NZ said it did not sign off workplaces as safe for work.

"The responsibility for ensuring a safe workplace rests with the company, not WorkSafe. We have been very clear that based on the short briefing our senior occupational hygienist attended, what information was provided did not give us any cause for concern. That does not, as stated in our advisory, amount to a sign-off from WorkSafe."

It had not launched an investigation into the health and safety considerations of the fire, and was in the very early stages of initial inquiries.

"If and when WorkSafe decides an investigation is warranted, we will advise media."