DIY Danger: Linseed Oil That Can Self-Combust

Aug. 5, 2010 — -- Under certain circumstances, a common household product can combust -- or catch fire -- without any outside flame or spark.

That product is linseed oil, which so many people use to stain their wood furniture or their fence or deck this time of year. It's a natural product extracted from flaxseed. Liquid linseed oil in the can is no more hazardous than any other oil. But leftover linseed oil on rags, paper towels and so on has the unique ability to generate heat as it dries -- sometimes getting so hot that it bursts into flames.

"GMA" tossed some linseed oil-soaked rags and newspaper in a box like any homeowner might. But we did it under the close supervision of Montgomery County, Md., Fire and Rescue. Then we trained cameras on our two experiments -- one outside, another in a fire lab -- and waited.

Charlie Shyab, a firefighter with the Washington D.C. Fire & EMS, says linseed oil fires seem to burn hot and fast.

And he should know.

Charlie and his fellow Washington, D.C., firefighters got trapped in a linseed-fueled fire. Their only way out of the house? Back through the flames.

"I did say to myself, you know, you can stay up here and try and put this fire out and probably die or you can get out of here," he told "Good Morning America."

They made it, but with devastating burns over much of their bodies. The official cause, according to the fire department? Linseed oil.

Back at the "GMA" experiment, after an hour and we checked the linseed-soaked rags with a thermal imager. Glow-in-the-dark spots on the rags showed where the linseed oil started to grow hot.

"Obviously you're getting the heat build-up in there," Donny Bord, a firefighter with Washington D.C. Fire & EMS, told "GMA."

Thermal probes we had attached confirm that the temperature has risen from 87 degrees to 110 degrees.

Here's how it happens: when linseed oil is exposed to air, it combines with the oxygen molecules. This chemical reaction creates heat. If the linseed oil is on something like a cotton rag, it can catch fire at as low as 120 degrees -- with no outside spark.