> On Nov 20, 2018, at 12:43 PM, Bruce Zenge  wrote:
> 
> Tony and All,
> I do believe you are right in your assessment that it all depends.  In the
> family business years ago, we used a lot of linseed oil.  On one occasion,
> we had a spill that was really messy.  Having lots of sawdust round, we
> proceeded to soak it up with the sawdust.  Dumped the whole mess in the
> trash barrels (55 gal drums cut in half), and looked away.  It was a warm,
> not hot, summer day and a couple hours later we smelled smoke.  Checked all
> over and finally found the drums smoldering.  We had a devil of a time
> putting that mess out, spending the rest of the day to get it done.  We
> had, on numerous occasions, cleaned up similar spills in the same manner.
> Obviously, there was something different this particular time.  Needless to
> say, we tried to be a bit more careful after that.  Never had another mess
> like that one.  And BTW, linseed oil and sawdust burns with a very
> unappealing odor.

Interesting.  That might have involved some sawdust that was already decaying.
Not for certain, but a possible explanation.  I spent four years involved with
several wood-waste-fired powerplant & sawmill operations a long time ago, and
one of the constant fire risks was with the wood waste from the chippers.  We
had to have large dozers and bucket loaders turning over piles of waste (10- 20
ft deep) on a relatively constant basis, especially near the boiler feed
conveyors.  Concerns were focused on warm days or after rainstorms (even though
they were relatively rare in that area), but the natural moisture content of the
wood chips was enough to initiate decay.  The smell of douglas fir waste wood
gets decidedly unpleasant when it starts smoldering too, and putting those
smoldering fires out is difficult and may take days.

In this case, you might have had another chemical reaction going on, in addition
to oxidation of linseed oil.  I can see where the heat produced by an exothermic
linseed oil reaction combined with the heat of decay of sawdust could have been
the difference.

I have never had a problem with ignition of BLO rags, but I’ve met people who
said they had a shop fire or lost their shop from not knowing it could happen,
and they strongly advocated submerging BLO rags in water in a closed can.   As
my shop is in my home’s basement, being careless in just the right circumstances
might make me homeless too.

Charlie