What to Know
Spontaneous combustion leads to an estimated 14,000 fires each year.
Oily rags not disposed of properly is one of the biggest causes.
It's best to lay any oily rags out on the driveway to dry naturally or put them inside a metal can with water away from the house.
A Maryland fire department is warning homeowners after numerous spontaneous combustion fire in recent years.
For Shannon Priddy, this will be the first full summer she and her family are in their new Potomac home, but there aren’t any knickknacks on the shelves in the living room, pictures on the mantle over the fireplace or school projects displayed in the kitchen.
"When you lose your house and everything in it, it takes a long time to fill up those shelves,” Priddy said.
The Priddys lost everything in a devastating fire in April 2014.
"While I'm in the shower, I hear my husband screaming, and then I hear him scream again, and he's screaming, ‘Fire, fire, fire!’" she said.
She and her husband got out of the house along with their kids and their two dogs.
“The only thing that happened that day that was out of the ordinary is we had contractors working on our deck," Priddy said.
The next day, fire investigators told her the fire started underneath the deck, the result of spontaneous combustion.
"It's a fire that is self-driven,” Montgomery County Fire and Rescue Battalion Chief Kevin Frazier. “It actually lights itself after some internal heating.”
Those types of fires are not uncommon, he said, and his firefighters have responded to dozens since 2015, including the Connelly School of the Holy Child in Potomac last May, a barn in Laytonsville in August, and a home under renovation on Horseshoe Lane in November that caused $750,000 in damage. Just last month, a massive blaze killed two dogs and displaced a family of four in the Potomac area. Investigators think that, too, was caused by spontaneous combustion.
"We do see a lot in single family homes when we have construction workers working on homes," said Frazier.
The News4 I-Team found spontaneous combustion leads to an estimated 14,000 fires each year according to the U.S. Fire Administration. Oily rags not disposed of properly is one of the biggest contributors, Frazier said. Priddy said workers had left rags used to stain the deck and other trash underneath the structure the day of the fire.
"When you're done with the rags as they begin to dry, they actually produce heat inside,” master firefighter Donny Boyd said. “It's a chemical reaction. So, if all that heat is compressed inside, it can't escape and gets higher and higher and higher."
To demonstrate, Boyd discarded a bunch of rags covered in a very common wood sealant into a plastic bag with newspaper and let it just sit in the sun. It started at 85 degrees in the center of the bag. An hour later, the temperature was 142 degrees. Two hours later, the temperature inside the bag was 358 degrees. Four hours into the experiment, the core of the bag sat at 345 degrees. Then seven hours into the experiment, the temperature inside the bag remained at more than 200 degrees.
When Boyd opened up the bag, burn marks were on the center of the rags.
“All of the materials were getting charred in the center," Boyd explained.
It's best to lay any oily rags out on the driveway to dry naturally or put them inside a metal can with water away from the house, Frazier said.
"Know the products that you're working on,” he said. “All of these products have labels on them.”
Priddy said she's now reading all the labels on any products she's using in her new home.
"It's such a simple solution that would have saved us a lot of pain," she said.
Learn more about spontaneous combustion fires here.
Reported by Scott MacFarlane, produced by Rick Yarborough, shot by Jeff Piper and Steve Jones, and edited by Jeff Piper.