File photo by Greg McCorkle
Firefighters try to save an Arbor Heights home in West Seattle on Aug. 27.

Science behind the Arbor Heights fire explained

Arson Investigator Ronald Ready spoke to the West Seattle Crime Prevention Council on spontaneous combustion by way of pyrolysis

Arson investigator Ronald Ready has pretty much seen it all when it comes to heat. Over the course of his 27 years with the Seattle Fire Department, 20 of those in the Arson and Fire Investigations Unit, he has investigated over 2500 fires and seen flames erupt in some very strange circumstances.

Ready brought his expertise to the West Seattle Crime Prevention Council meeting on Oct. 18 to explain the science behind the Aug. 27 Arbor Heights fire on 41st Ave S.W.

The fire was ruled accidental by way of spontaneous combustion. Material left in a portable fire pit that had been stashed in a garage for two years suddenly burst into flame on a hot August day, fully consuming the house before firefighters were able to subdue it. The family was gone camping.

In the aftermath, questions were raised about sufficient water pressure to fire hydrants in the neighborhood. Responding firefighters were forced to spread their supply lines over a four to six block radius in order to get enough water (more on that later).

How the fire started
“Spontaneous combustion is an interesting phenomenon,” Ready said, “and it only happens with organic materials.”

Pyrolysis – “nothing but a fancy word meaning decomposition of a solid material through the application of heat,” he said, is the guiding science that starts the process. He told the crowd to imagine putting their hand into a compost pile. That’s pyrolysis at work, and sure enough, it will be warm.

Ready investigated the home’s ruins and found no signs of arson. In talking to neighbors he learned the first to call 911 saw the garage door ajar with smoke and flame inside the garage.

He talked to the homeowner who said he hadn’t used the fire pit in two years and wasn’t sure what was inside. He had stored it away and piled some blankets on top.

Looking into the fire pit, Ready said he found no charcoal, only charred wood residue. Earlier in his investigation, he found piles of scrap wood including cedar in the backyard.

“Sometimes the wood is pretreated,” he said. “And sometimes the wood is pretreated with organic material like linseed oil, sunflower oil, a ‘green’ deck stain … it has to be organic in nature.”

Ready’s theory began to form.

“Once you have organic material in a pile … and put blankets over it,” he said, pyrolysis will kick in over time and prime the wood to more easily ignite.

“The ambient temperature was about 90 degrees and it got later in the afternoon … a gradual buildup of heat,” he said.

“It’s baking in there and then you have some kind of wood cellulose and possible organic stain or something in the fire pit, and that’s what caused the fire.”

Ready, who also trains others in arson investigations, used another analogy to drive the point home.

“Think about this, you have a candle – brand new candle, brand new wick. Everybody knows how doggone hard it is to light that, you have to hold that flame on that wick to get it lit,” he explained.

“Use the candle, blow it out and come back the next day. Light that same match or lighter and you are not even touching the wick. What happens is the heat is breaking down that material through pyrolysis and it begins off-gassing with vapors. The flame ignites the vapors and “it almost jumps to the wick.”

“Why does it light so readily? Because it’s already in a charcoal state. Its ignition temperature has been lowered dramatically because it has been pre-burned. Very much like the portable fire place that was put in the garage after being used over and over again.”

His investigation also concluded the garage door had popped open on its own. The heat built up to a point where it short-circuited the automatic door electronics, causing it to rise.

What happened with the fire hydrants?

Ready said the Arbor Heights neighborhood firefighters responded to has a four-inch elevated water main that, “might have been fine for your house, but it wasn’t enough for drawing water through the (fire) engine.”

Ready wasn’t at the fire initially, but said he listened to radio communications throughout so he was aware the first fire hydrant simply didn’t work and the second one a block away had insufficient pressure. This forced the SFD to spread supply hoses over a five block radius to get enough water pressure to the engines.

Seattle Public Utilities (who runs the water in this town) “said the fire department doesn’t know what they are doing, there is nothing wrong with that hydrant – they put that right on the Seattle Times front page,” Ready said. “That doesn’t make us happy when they throw us under the bus like that … the water main is too small to supply the area and they know it.”

SPU later issued a press release admitting the first hydrant was inoperable and said the water main for the neighborhood was too small, but lack of funds prevents them from fixing it, Ready added.

More fire safety tips from a guy who's seen it all

Before wrapping up his presentation to the council, Ready passed on a few more surprising causes of fire.

He’s seen fires at downtown day spas where customers were given massages with organic oils and given a towel afterwards. The towels were discarded and collected by staff, washed, dried and stacked on top of each other in towel racks. The organic oils were not fully washed out, there was plenty of heat and whoosh – a fire ignited.

He’s seen it happen at home. “We have a cooldown cycle on dryers for a reason,” Ready said, adding even cooking with vegetable oil that splatters on your clothes can be a danger if brought out of the dryer hot and then stacked.

Coming into Fall, he told everyone to, “Think about your thermostat knob for a second. If you turn it all the way to the left you think it’s off, right? It’s not off.”

Thermostat knobs general stop at 55 degrees Fahrenheit on the low end, so if the temperature drops below 55, the heater kicks on, he said. Ready investigated the death of a 36-year-old man after a pillow resting against a baseboard heater ignited with the heat tuned “off.” The man did not have a smoke detector.

A precautionary tale

“I always heard the perfect arson fire was to put some grease on the stove and go to the store,” a crime prevention council member said.

“Ya, but you gotta be smart about that,” Ready responded.

Early on in his arson squad career, Ready said he responded to a house fire that destroyed a kitchen. The middle-aged woman was distraught and blamed it on a grease fire.

“Well, ma’am, what were you doing? It looks like what we call a food on the stove fire,” Ready said.

“Well, I was cooking potatoes for my hubby.”

Ready started his investigation, as he always does, outside the home. He worked his way back to the kitchen.

“She’s cooking potatoes for her hubby and we didn’t find a doggone potato. Not even in the freezer did she have a potato,” he said.

Confronted with the lack of potatoes, the woman fessed up. Her friend had recently installed a brand new kitchen, making her jealous. She decided to start a grease fire in order to accelerate her own new kitchen.

Ready said the woman was charged with first degree arson – a serious felony with a maximum of 20 years and a minimum of 43 months in prison in Washington.

“Anyone thinking about remodeling?” he asked.

“Don’t do that.”

The West Seattle Crime Prevention Council meets on the third Tuesday of each month at the Southwest Precinct at 2300 S.W. Webster St. There next meeting is on Nov. 15 when Chief of Metro Security Lisa Mulligan will stop by.

On a similar note, the West Seattle Blockwatch Captains’ Network meets one week later at the same location (fourth Tuesday of the month). WSBCN’s next meeting will be in January as the next two months coincide with Thanksgiving and Christmas week.

Both are open to the public.

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