Mr Ducker said the company would re-start operations once it had full clearance. Yesterday's incident was the fault of a particular valve.
In February 2015 the thermally modified timber plant was shut down because of rashes and other ailments which staff and neighbours feared were caused by emissions from the new timber heating system.
The discovery of engineering issues meant the kiln was shut down in April 2015 for all but testing purposes.
In August, authorities said tests showed levels of air pollutants were well below recommended guidelines when the kiln was operating normally.
But they suggested acrolein and acetic acid levels could exceed standards if a burner used to eliminate noxious gases stopped working during the kiln operation.
The kiln had been operating for the past few months with no issue, Mr Ducker said.
The $2.5 million kiln was introduced in April 2014.