He was in the shower, but would quickly discover the adjacent bedroom was ablaze.

Smoke was already visible from the nearby fire station when crews were called to the Rocherlea home just before 8am on Thursday.

A bedroom at the back of the Ferntree Court house was internally engulfed in flames while smoke had spread throughout the other rooms. The fire was contained to the bedroom.

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"The end of the bed and all the carpet was on fire," Kaidan said. "So I got my sister, who was in the bedroom ... [and] took her outside."

"Then I had to go and get the dog, so I brought her up the hill - which was a little bit difficult because she refused to move - and then I went back in with the hose to try and put it out."

It was then the Brooks High School student discovered just how fast the fire had grown.

"When I got back in there and actually saw it ... the whole room was on fire pretty much," he said.

His efforts to extinguish the blaze saw the water itself catch fire, with firefighters suggesting to him there could have been an accelerant present.

"The water when I sprayed it in there wasn't actually doing anything," he said.

"The whole back half of the house is all burnt up really - so within about five minutes it caught up really quick."

The cause of the fire is still unknown, with the fire service handing investigations to Tasmania Police.

Tasmania Fire Service Rocherlea station officer Roger Whittle said there was an attempt to put out the fire using buckets and a hose, and a woman singed her hair.

One fire unit from Rocherlea and one from Launceston arrived at 8.02am and extinguished the fire, which caused extensive damage to the house's rear.

Ambulance crews also attended to treat one child and a woman for possible smoke inhalation. The other six children avoided injury.

Despite the ordeal, Kaidan shrugged off suggestions of bravery.

He hoped to be able to return to school on Friday to see his friends - and arrange to catch up on an exam he had been due to take on Thursday.

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