A chimney, doing exactly what it is intended to do.

Veteran firefighter Murray 'Moe' Stevens was left scratching his head.

The Waihi chief fire officer and his team had been called to a roof fire on Johnston St, Waihi, about 12.45pm on Sunday.

They found an old wooden rental with smoke pouring out of the ceiling cavity.

But Stevens couldn't quite figure out where the heat was coming from.

READ MORE: Homeowners reminded to clean chimneys before winter after fire

He saw the fire burning in the fireplace, as it should.

Next, he went outside to make sure the chimney was in good working order.

If there had been one, the smoke would have drifted out as it did from thousands of others across the country as the land frosted over.

The shivering tenants had two options in the house - an old open fireplace in one room and a more modern wood burner in another.

They chose poorly.

"It's a first," Stevens said, "it doesn't happen often but that's what it is - there was no chimney."

The flue from the open fire place rose vertically up, as per usual, yet it terminated inside the ceiling cavity.

There was no way for the smoke to escape. It pooled - thicker and hotter - until it combusted.

"We had to get the roofing iron off and put it out," Stevens said.

"We were a little bit lucky. One of the people there stood on a step ladder with a garden hose and kept spraying it on the gable end of the wooden house.

"That slowed it down a wee bit and we were lucky enough to get up there and get it open and get it out."

The fire caused damage to electrical wires and a water tank in the crawl space.

Stevens did not know if the renters knew the fireplace was unusable.

"It has been pretty frosty weather in the last week and they lit a fire in the old fire place which was not blocked off.

"I suppose you don't go around and have a look if you've got chimney. If you've got a fire place, you assume you have got a chimney."

On Sunday, Northern Fire Communications shift manager Jaron Philips said the ceiling space filled with smoke.

"It eventually just combusted," Phillips said.

Everyone got out safely.

It was the first time he had heard of people lighting a fire in a fireplace that had no chimney.