AUSTIN (KXAN) — The Austin Fire Department has a warning as you crank up your home’s heat sources during cold weather.

AFD says it’s put out two fires in the last 24 hours. One after a space heater was too close to a combustible. The other — a surprise problem in a homeowner’s chimney.

Austin Fire Division Chief Thayer Smith says the fire at a home on Westlake Drive was caused because there wasn’t enough room, or clearance, between the flue and the chimney chase. He says part of the flue was actually touching the wooden enclosure and, through a process called pyrolysis, caught fire.

“The wood actually breaks down and kind of turns to a charcoal like substance over years and years of being heated,” Smith said.

This picture shows part of the chimney flue touching the wood enclosure, which is now charred after the fire. (Source: Austin Fire Department)

“I had never thought of that. We’ve been having fires in this chimney since 1997,” says homeowner Phillip Berry, who says they lit their first fire of the season Thursday night.

After a couple hours, Berry said his wife, Susan Landers, got a phone call from their fire alarm company that there was a fire upstairs.

“She went upstairs, and she said, ‘It’s really smoky up here!’ And the lady’s telling her, ‘Get out of there, Get out of the house!'” Berry recalls. “When she came down, she said, ‘I could hear — I could hear the fire crackling behind the wall.’ I went, ‘Oh! We’ve got to get out of here!'”

Berry showed KXAN around his home on Friday. Firefighters had torn down the chimney wall upstairs, where the fire started. The carpet is soaked from fire hoses, and there is debris from insulation, as well as drywall all over the floor.

Smith says current code requires at least two inches of clearance between a flue and its surrounding, depending on the type of chimney, flue and materials used.

But he believes that minimum is not enough — especially when the chimney chase is not made of stone or brick, which he says is more common in other regions.

“Around here, you see a lot of wood, wood chimneys with low clearances. And just over time, that’s just a recipe,” Smith says.

So, if you’re building a home, Smith says it’s a good idea to ask for more clearance than what is required — at least six inches, depending on materials used.

Berry and Landers agree.

“I think it would be prudent for people buying a house, new or old, to try to understand… how their fireplace and chimney are constructed,” Berry said.

The couple says their smoke detector saved their house — and possibly their lives.

“I am so thankful my house did not burn down,” Landers said.

AFD is reminding people to make sure all their smoke alarms are working, and maybe put one closer to your chimney.

The Chimney Safety Institute of America says a trip to your attic can give you a view of your clearances but say homeowners should never inspect their chimney, fireplace or venting system themselves, and should instead call a CSIA certified chimney sweep.

The couple is not canceling Thanksgiving with their family just yet, hoping to have their electricity restored in time.