An Auckland pathology laboratory has lost its accreditation for examining tissue samples because levels of a toxic gas got so high staff had to be evacuated almost daily.

Auckland District Health Board's LabPlus had its histology accreditation suspended on June 9 after repeatedly failing to fix ventilation issues which were first raised in 2002, soon after its new facilities at Auckland Hospital were opened.

Histology is the microscopic examination of tissue in order to study the manifestation of disease.

A letter from International Accreditation New Zealand (IANZ) to LabPlus stated factors taken into account included almost daily staff evacuations due to formaldehyde exceeding statutory workplace exposure standards and that senior staff were unanimous in their belief the conditions presented a risk to "clinical safety".

According to the Worksafe New Zealand website formaldehyde's short term health effects included irritation of the eyes, nose and throat. The gas was a skin irritant and a strong skin sensitiser which meant once a person was sensitised further exposure could cause intense responses, even at low concentrations.

Long term exposure to formaldehyde, which was classified as a carcinogen in New Zealand, could result in changes to the cells it regularly came into contact with.

The IANZ letter said issues around space and ventilation in the lab continued to be raised in reports which lead to a strong recommendation in 2015 and then a corrective action request in 2016. It had not been corrected by an assessment in March 2017 so a further month was given to fix it but by June 7 no changes had been made.

Association of Salaried Medical Specialists executive director Ian Powell said it was a "calamity" and an indictment on the heath board's leadership.

"If they had listened to their pathologists in the first place they wouldn't be in this position," he said.

He said lab results affected 70 per cent of the clinical decisions in a hospital and the accreditation suspension was putting pressure on the laboratory staff to continue to produce results in a timely fashion.

An Auckland District Health Board spokeswoman said the organisation shared the IANZ concerns because health and safety was a priority.

She said the amount of formaldehyde was monitored rigorously and if it surpassed workplace exposure standards, alarms alerted the employees and they were instructed to leave the area. Staff also wore safety gear to minimise exposure.

Formalin, the liquid version of formaldehyde, was used to store many of the specimens analysed in the laboratory but because the service had been experiencing increased demand, more samples stored in the liquid were processed.

Earlier this year the board approved the budget and awarded the contract for an expansion of the laboratory space for histology and enhanced air extraction technology but it was not scheduled for completion until December which IANZ was not happy with, the spokeswoman said.

Temporary changes had been made and a reassessment had been requested. If IANZ found the changes satisfactory, the suspension would be lifted.

The spokeswoman said the suspension only affected externally contracted work, about 15 per cent of what the lab did. The contract work had been diverted to the health board's other facility in Mount Wellington so none of the services had been affected.

She said all histology tests were still meeting clinically agreed time targets.

-NZ Herald