Homeowners staining their deck or garage before winter may not realize they’re dealing with chemicals that can all too easily ignite.

From Orono to Robbinsdale, metro area fire departments are responding to an increasing number of fires started by spontaneous combustion of rags soaked in stain or oil.

Firefighters across the state are seeing the same problem, with crews reporting at least 27 of these types of fires so far this year in Minnesota, according to the state Department of Public Safety.

It’s prompting a new warning this week to homeowners to be aware of the problem and more safely discard oil-soaked rags, which can heat up and spark a fire, quickly engulfing a garage or home.

“I’ve never seen anything like this where we’ve seen so many of them,” David Gustafson said of fires started by spontaneous combustion. He’s supervisor of the Hennepin County fire investigation team. “It’s that time of year people are out staining their decks. You’ve got to be careful when you’re working with this stuff.”

Gustafson has seen the ramifications firsthand as a firefighter in Robbinsdale and Golden Valley and as the investigator with the county team. Since Memorial Day, he’s responded to about eight fires started by spontaneous combustion. One weekend, the team responded to two fires at homes in Orono just a few miles apart, both likely ignited by stain rags, he said. Another one recently in Corcoran left a garage burned to the ground, he added.

“They just don’t think something like that can happen to them,” State Fire Marshal Bruce West said.

Safety tips

According to the state, Minnesota has had 312 fires started by spontaneous ignition since 2010, most commonly in homes. The fires often started in storage areas or garages by oil-soaked rags used in wood staining, the department said. But people can easily prevent the fires, West said, by allowing rags to completely dry before discarding, soaking them in water and then drying, or placing them in a metal container with a tight lid.

“They’re very preventable,” West said. “We just want people to realize what can happen.”

Luckily, in Hennepin County, Gustafson said, none of the fires he’s responded to has resulted in injuries or deaths. Instead, embarrassed homeowners are shocked to find out that a few discarded rags could cause such a big fire.

“Within a couple of days or so, it can heat up and combust,” he said of stain rags. “People don’t understand what spontaneous combustion is. You can’t just throw them in the garbage and walk away.”