Firefighters surveyed by their union say they weren't given proper breaks and had inadequate training to cope with the SkyCity convention centre fire in Auckland last month.
Martin Campbell, the Professional Firefighters Union's Auckland secretary, said they have received 133 survey responses from the about 150 firefighters that have fought the fire.
"Eighty-one percent of firefighters are reporting issues with fatigue management, lack of rotation, no ability to have breaks or rest, working extremely long hours - 18, 19 hours plus," he said.
Mr Campbell said they have got two reports on firefighters falling asleep at the top of tall ladders "about eight-ten storeys up in the air".
"As you can imagine, if firefighters are falling sleep at the top of those after having to working a 19-hour shifts, they must be incredibly fatigued and tired to fall asleep in that kind of dangerous situation," he said.
Firefighters also reported they had to urinate in the street and buy their own food, according to Mr Campbell.
"After five days, there were still no ablution facilities being organised by Fire and Emergency (FENZ) to be sent to the fire ground," he said.
"Firefighters had to knock on the doors of private businesses and residences, asking to use their toilets. At one stage, they even had to ask Fletchers, whose building that was on fire, to use their portaloos inside the building."
The survey also found close to 80 percent of respondents said they had not received adequate training for working on a roof and using of tools.
Mr Campbell said the full survey has been presented to FENZ.
"Hopefully FENZ will take on board the concerns that have been highlighted and find solutions quickly," he said.
Ron Devlin, Auckland region manager for FENZ, said the negative feedback was a "great opportunity" for the organisation to learn and improve.
He said they're aware of some of the issues and are investigating. He said they will talk to individuals to find out more.
Mr Devlin said falling asleep high up in the air was "unacceptable" and "terrible" if it's true and they'll work to find the cause and prevent it from happening in future.
He said though normal ablution units were not available at the start, toilets were made available in buildings around the site.
He also said there was a lot of food on site but it may have run out at a certain point, and a "working at heights" training package has been rolled out to Auckland staff extensively. Firefighters who have concerns should talk to their managers, he said.
"The safety of our people is paramount. We're up to looking at anything that contributes to improving the way we operate and looking after the men and women of Fire and Emergency New Zealand," he said.
"This was a very large and complex event, a large number of our women and men have done an absolutely spectacular job. We've got every reason to be proud of the work they've done.
"We've got some great feedback and this is the learning feedback that we get. It's a positive thing to move on with and we'd like to learn as we go forward."