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Linseed oil, a common wood polish and sealant, can burn your house down in minutes if it's not handled properly.

The product can spontaneously combust and mishandling it can be as simple as tossing some rags and newspapers, soaked in linseed oil, in a box, as ABC News did for an experiment.

Mike and Sherri Prentiss of Cincinnati know the dangers of linseed oil firsthand. They left some rags in a bundle.

"I had put it sort of folded on itself in to a corner of the garage," Sherri Prentiss told ABC News. "That was about 5 p.m., and by 9 p.m. that night our garage was on fire," she said. "There were flames shooting 30 feet into the sky."

In our experiment, a thermal imager revealed glow-in-the-dark spots where the linseed-soaked rags had reached 110 degrees after an hour. After two hours, there was smoke curling from the newspapers and rags. And after three hours there were flames.

Linseed oil is safe for wood because you spread it out, but left wadded up on rags or paper the oil is so concentrated that it heats up as it evaporates. One of America's biggest high-rise fires, in Philadelphia in 1991, was caused by workers who didn't clean up linseed oil properly. Three firefighters died.

So how can you protect yourself?

Some experts say spread linseed-oil soaked rags flat on your driveway until they are totally dry. To be even safer, you can fill a metal can with water, put the rags in, and then seal it up tightly.