boiled linseed oil BLO

As someone else stated, BLO is no longer boiled to get an initial polymerization. Today, metal catalysts are added. The polymerization gives off heat. This heat can be enough to ignite a rag if it is crumpled up. If the rag is spread out, the heat will dissipate into the surrounding air. I just hang my BLO rags on a chain link fence and then toss them with the regular trash the following day. Once polymerized, BLO is not going to give off any heat to cause a fire.

Please keep in mind that an office building in Philadelphia lost several floors to BLO contaminated rags that were thrown into a closet before they had a chance to fully cure / polymerize. The heat generated from polymerization was enough to ignite the balled up rags.

Good Luck