Spontaneous combustion in a basket of freshly laundered towels caused a blaze which could have destroyed a row of Kaikohe shops.
The incident has prompted a safety warning from the town's fire chief, who says spontaneous combustion is a "very real risk" to commercial laundries but also to people doing their washing at home.
The alarm was raised by the owner of an Indian restaurant on Broadway, Kaikohe, who smelled smoke about 6.45pm on Thursday. He searched his shop for the source before realising it was coming from the closed Presto Laundromat next door.
Kaikohe fire chief Bill Hutchinson said the laundromat was full of smoke when the brigade arrived. Firefighters forced the door, dragged the burning laundry basket outside, and ventilated the building.
It was fortunate the fire started while the restaurant was still open and the brigade was able to get there quickly. If the blaze had started later that night both shops could have been destroyed and Kaikohe would have lost two more businesses.
Mr Hutchinson said few people understood the danger of spontaneous combustion, especially in commercial laundries. If cotton was folded and stacked up while still hot from the drier, the heat could be enough to trigger oxidation. Heat released by the oxidising cotton gradually built up until it was enough to start a fire. The same was true of linen, he said.
The risk was greatly increased if there were any traces of cleaning products, oil or fat left in the fabric to feed the fire. Washing did not remove all oils, Mr Hutchinson said.
Spontaneous combustion typically occurred in piles of tea towels, overalls or cleaning rags. In this case the cause was massage towels which, even after washing, held traces of massage oil. Freshly folded washing was often kept in plastic or cane baskets, which then added to the fire.
Mr Hutchinson advised allowing laundry to cool before folding and stacking.
"I know that efficient people like to fold washing right away after it's been in the drier to reduce creasing but it has to be allowed to cool down first."
Some driers came with a cooling cycle for that purpose, he said.
Spontaneous combustion could also occur at home or while washing was still in the drier. He had been to several house fires which had started in fresh laundry.
The most dramatic example of spontaneous combustion Mr Hutchinson knew of was the blaze which destroyed the brand-new Kaikohe Memorial Hall in 1957, one week before it had been due to open. The cause was a pile of rags used with linseed oil.
Presto Laundromat owner Moengaroa Floyed said she knew the danger of spontaneous combustion, and normally she draped towels around the shop if she knew the owner wasn't going to pick them up the same day. In this case, however, she had been preoccupied with moving house,
"I took my eye off the ball."
She knew what had happened as soon as she smelled smoke on her way back in to town that evening.
She was grateful to the firefighters and her neighbours at the Pizza Place and Indian Takeaways.
Other examples of spontaneous combustion include a fire at Carrington Resort on Karikari Peninsula in 2015 (tea towels), a kitchen fire at Toll Stadium in Whangarei in 2014 (tea towels), a fire which destroyed a large shed at Waikino in 2013 (rags used for oiling furniture), and a Kerikeri laundromat fire in 2003 (freshly washed clothing).
The fire which destroyed a Kerikeri laundromat last year was caused by an electrical fault.