Fire is chemistry lesson for homeowners

Spontaneous combustion from rags and solvents ruled as cause

The Sunday morning house fire that displaced a family of five in Palmer Township has been ruled accidental, officials said, and its cause comes with a warning to homeowners everywhere.

Palmer fire Deputy Chief Jim Alercia said rags and paint brushes inside the home on the 3700 block of Timberlane Drive, used for staining a day earlier, spontaneously combusted with flammable objects nearby.

From there, the fire spread rapidly.

“The fire had already spread across the rear of the home and into the attic before firefighters were even alerted of the incident,” Alercia said.

“Spontaneous combustion” reads like an exceedingly rare chemical phenomenon, and indeed it is for most household objects that come up in a quick internet search: charcoal, pistachio nuts, cooking oils.

But paint thinners, waxes, linseed oil — any solvent used for wood finishings and varnish — “these are the ones you should be worried about,” said James Dickerson, chief scientific officer at Consumer Reports.

Four other fire departments helped Palmer Township crews battle the blaze that broke out at 5:30 a.m. Sunday in the township’s Old Orchard section. They contained the fire to the attic and back of the bilevel building, but smoke and water damage rendered the house

uninhabitable for the family of two adults, three kids and a dog.

Neighbor Gina Falco set up a GoFundMe page to collect monetary and clothing donations for the family, which as of Wednesday has raised more than $6,700.

Combustible or flammable liquids cause more than 55,000 house fires a year in the U.S., according to data collected between 2007 and 2011 by the National Fire Protection Association. About 16% of those are caused by the class of liquids that includes paint thinners and varnishes.

Though cooking and lubricant oils caused most fires in the data collected by the NFPA, whether by misuse or because of some stimulant, they are much less prone to spontaneous combustion. Cooking oils and charcoal, for example, are fairly stable on their own, said Dickerson, a former physics professor.

But all volatile solvents like paint thinners or wood stains need to spark a runaway reaction is some oxygen, heat and other combustible material.

“Because these solvents are often cleaned up with rags, that’s a combustion right there,” Dickerson said.

The severity of the fire depends on the temperature of the room, the type of oil and how tightly packed the rags are, Palmer officials warned in a news release.

When solvent-laden rags dry, oxidation occurs simultaneously. Oxidation is a chemical process in which an element gains electrons from the oxygen surrounding it. In the case of iron, this results in rust.

But oxidation is an exothermic process, meaning heat is released as a result. With particularly reactive substances, releasing heat is bad news: a self-heating cycle that gets out of hand.

In the case of the solvent and the rag, as both materials are exposed to oxygen and release heat, their temperatures rapidly climb to a point at which they can ignite. The solvent is likely to ignite first, causing the rag to catch fire.

“It can be dramatically exothermic,” Dickerson said. “There’s a lot of heat that’s going be generated from this oxidation process over a relatively small volume. That can heat up extremely quickly.”

Even laying oil-soaked rags to dry outside in the sun isn’t the most safe way to dry them out, because the sun can be yet another heat source, he said.

The best way to dispose of them is to douse them in water, put them in a nonflammable container such as an old paint thinner can, and close the lid.

Those who choose the laying-out method should use metal surfaces and avoid too much sun exposure. It may take two full days or longer to completely dry, Palmer Township officials advised.