The risk of asbestos inhalation during the Waikeria Prison riot earlier this year may never be known because the Department of Corrections rushed to clean equipment before testing it.
Corrections has confirmed there is asbestos in the soon to be demolished building, but said it is satisfied that the risk of exposure to both staff and inmates would have been low.
But the union for prison officers is not convinced and said it is sending an uncleaned kit, used during the peak of the riots, to Australia to be tested.
Aerial footage of the jail after the riot shows charred remains, the roofs are burnt through and caved in, making it much too dangerous for staff and emergency services to enter.
Even now, months later, access inside the building's perimeter is rarely permitted, especially as it is designated a contaminated site because of the known presence of asbestos.
That means both guards and prisoners may have been exposed during the January riot.
Following the six days of fire and damage, Corrections was concerned about potential exposure, and asked the officers to have their kit cleaned and decontaminated.
Corrections Association president Alan Whitley said that was a problem - because now they have no idea what the levels of exposure could have been.
"Instead of getting the equipment tested to get a baseline to see what was on it, all they've chosen to do is clean it to get rid of any evidence that's on it.
"They've got a couple of articles tested to show that the cleaning worked. But what we're concerned about is what was the level of asbestos that was on that kit first?"
Whitley said the officers who were involved in the riot were angry and worried about the risk of exposure.
They were in the thick of the smoke for many hours.
"It's not just breathing it in, our members would have been handling that kit. They were also eating, they were there for days and days on end.
"So it's not just what they were breathing in, it was what was on their vests and their uniform that they were then touching and then touching food and drink as well as their face."
However the Department of Corrections said expert advisors told them there was a negligible risk of disease for inmates and prison officers.
"We have been advised that short-term, low-level exposure to asbestos poses a negligible risk of disease.
"The duration of the event and the subsequent access of the top jail would be considered a short-term exposure, and the face masks provided would have adequately protected our staff."
It said testing of the kits, after they had been decontaminated showed no asbestos present.
Around 200 inmates were in the area at the time of the riot and had to be moved away from the danger.
Corrections said they had all been told the potential risk was extremely low and were able to see health services if they had concerns.
"Given the low risk we did not carry out any testing of clothing or require medical checks."
Whitley said he has one vest worn during the height of the riot which was not decontaminated and is now being sent to Sydney for testing.
He said the results of that might prove there was nothing to worry about, but the exposure possibility should have been ruled out much earlier by the department.
National's Corrections spokesperson Simeon Brown said the whole situation was unacceptable.
"Corrections has admitted that there is certainly asbestos in the building.
"And so with a fire which was ongoing for six days due to rioters, it would make absolute perfect sense to actually just test to work out what level of exposure or potential level of exposure was to those involved so that they could get the right support if needed."
WorkSafe confirmed to RNZ it had also not been made aware of any potential exposure.