'Spontaneous combustion': Linseed oil possibly to blame for San Tan Valley home fire, officials say

'Spontaneous combustion': Linseed oil may have caused San Tan Valley house fire

A San Tan Valley home went up in flames after rags soaked in linseed oil spontaneously combusted in the garage, according to Rural Metro Fire.

SAN TAN VALLEY, Ariz. - Officials with the Rural Metro Fire Department released details surrounding a house fire in the far East Valley that possibly started as a spontaneous combustion.

According to a Facebook post made on April 26, the fire happened late on April 25, and functioning smoke alarms at the home alerted residents to the fire, all of whom were able to safely evacuate from the home.

"Initial reports indicate possible spontaneous combustion of shop rags coated with Linseed oil as the point of origin," read a portion of the post.

Rural Metro officials posted aftermath photos of the home, which showed heavy damage to the home's roof, as well as damage to at least two vehicles at the scene.

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Photo showing heavy damage to a home following a fire in San Tan Valley on April 25, 2022. (Courtesy: Rural Metro Fire Department)

What is Linseed oil?

According to the Department of Fire & Emergency Services in Western Australia, Linseed oil is an oil obtained from the dried, ripened seeds of the flax plant, and it has a variety of uses, including as an impregnator and varnish in wood finishing.

"Linseed oil is still widely used for the finishing and refinishing of furniture and timber products," read a portion of a document on the hazards of Linseed oil, which was published by fire officials in Western Australia.

Why can it spontaneously cause fire?

The document states that when Linseed oil is drying, heat is generated, and in some cases, this heat may be enough to ignite the material it is on, and then anything else nearby, in a process known as spontaneous combustion.

"For spontaneous combustion to occur, enough heat must accumulate so fire can start. You would never see a piece of furniture spontaneously combust because the oil oxidizes in open air, so the surface never even gets warm to the touch, but a pile of oil-soaked rags can," read a portion of the document.

The document states that in cases of spontaneous combustion involving oil-soaked rags, the rags act as an insulator as the oil generates heat via oxidation.

"The rags act as an insulator, allowing the heat to build up until the cloth smokes and eventually ignites. The bigger the pile, the greater the possible heat and the greater the risk," read a portion of the document.

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What should I do?

Fire officials in Western Australia say rags or other applicators used with Linseed oil should be allowed to dry in a safe place, away from flammable materials, with the best way being to lay them out on a concrete driveway or other non-combustible surface, and allow them to dry off completely.