View Full Version : Spontaneous Combustion

Per Swenson
05-13-2005, 7:39 AM
I just read the thread on oily rags and felt the
need to post this ancedote.
Spontaneous combustion just never really happens,
at least not to me. Heh, Heh,heh.
I get the call, Per would you come over and take a look at my
freshly Polyurethaned floor, it just won't dry.
Sure I said, but how long has it been?
10 days was the reply. Uh oh, I will be right over.
The homeowner had put the poly on way to thick.
The poly just skim hardend on top, leaving a nice jelly
in between. He was desperate about what to do.
It was his living room, and he was now living in the kitchen.
He did not like the Idea of waiting say 3 months for the floor to cure.
He needed it fixed now.
Off to the rental center for a floor drum sander.
90 minutes later he had bare wood.
And a funny smell.
You did not lose a ciggarrete did you?
Nope. That is when I noticed the tiniest whisp
of smoke from the saw dust bags.
Out the door they went,(there was about 18 inchs of snow on the lawn),
One after another they ignited, from a wisp of smpke to fully
involved in 30 seconds. Remember it was in the snow, melted right through
to the lawn then smoldered for 12 hours.
Real disaster was barely averted.
And I always thought that stuff never happens to me,
yeah right.
Floor came out fine with THIN coats and all is well.

Jeff Sudmeier
05-13-2005, 8:33 AM

Way to think on your feet! Literally! Good have been a REALLY big mess!

John Hart
05-13-2005, 8:44 AM
Guess I better clean the shop today :rolleyes:

Jason Roehl
05-13-2005, 9:13 AM
I think it would be important to note that in this case, the not-yet-dry poly and all its solvents were probably the main cause of the fire. The sanding process probably generated just enough extra heat to get the ball rolling, and the poly's solvents that had not yet evaporated were just fuel for the fire. Normally, when fire in sawdust bags happens to floor refinishers, it's a smoldering fire that takes hours to really get underway. I know of one guy who left the bags in his van overnight, and didn't have a van the next morning. Another time, one refinisher on a job where I was painting tossed a cigarette into a sawdust bag and went to lunch (it was in the back of his truck). Later, they smelled smoke, and it took a while to dig through all the sawdust to find the offending embers, but it was only about the size of a golfball after a couple hours. When I refinish floors, the sawdust always goes in garbage bags at the end of the day, and the garbage bags stay outside away from any structures or vehicles.

David Fried
05-13-2005, 10:04 AM
I must admit I like finishing when it's raining out just so I can toss the rags out onto the stone patio and know they'll be OK.

Per Swenson
05-13-2005, 10:46 AM
Maybe I wasn't clear,
Jason, I am fully aware of the cicumstance behind the inferno.
Indeed , I was aware of the possibility in some far recess
of my brain. The point was, "this never happens to me".
A dangerous mindset akin to always running yellow traffic
lights and never having a accident.
It was also meant to note a sort of professional complacency
which can and will lead to disasterous consequences.
A mind set I can ill afford.

Ken Fitzgerald
05-13-2005, 11:10 AM
Per....it's not a matter of "professional complacency" it's a matter of "safety complacency" a mindset that all of us cannot afford to have. It's important that all of us, pros and DIYer's like myselff learn from your lesson. Thanks for posting!

Jules Dominguez
05-13-2005, 1:37 PM
I've read some scary posts about spontaneous combustion incidents, but I haven't seen a complete description of exactly how and why it occurs. Several of the posters have described good practices, but not the complete reasons for following them.
Spontaneous combustion is combustion that occurs in a material without any outside source of heat or ignition. It occurs frequently in piles of wood waste at wood plants and paper mills, and in large coal piles at power plants. I'm familiar with those and I think the oily rag fires occur for the same reasons.
Three things are needed to cause spontaneous combustion - air for oxygen, an oxidizable or combustible material, and insulation to hold in the heat from oxidation until the temperature rises to the point at which the given materials will combust.
Wood waste and oily rags both have a lot of surface area relative to their volume or weight, so they oxidize and generate heat rapidly. A pile of wood waste or oily rags provide their own insulation - heat builds up in the center of the pile.
Air is obviously present unless you submerge the rags in water. A closed can may or may not prevent combustion. The closed can may contain enough air for combustion to occur, or it may allow enough air to leak in. Putting oily rags in a closed can is not necessarily completely safe.
Spreading the rags out, whether it's done indoors or outdoors, will prevent heat buildup. Just to be completely safe, though, I'd spread spread them outdoors.
Putting the rags in a can of water is a temporary measure. I don't know if this makes them less susceptible to oxidation after the water evaporates, but I suspect it doesn't.
Drying oily rags on a chain link fence or a bush, with or without the prior immersion step, probably allows most of the oxidation that's going to occur to do so, thus reducing or eliminating the possibility of future spontaneous combustion.

thomas prevost
05-13-2005, 3:17 PM
Having done some research for Minwax, The major culprit is the initator or catalyst put in BLO, tung oil and poly. It accelerates "setting" or hardening of the material. This reaction give off heat. When painted in a thin coat on a large surface. i.e floor the heat is dissipated to the air. But in a confined space, the heat is trapped and in turn helps accelerate the reaction until enough heat is generated to cause fire. The solvent becomes the fuel.

Placing in a bucket of water stops this as the water abosrbs the heat or placing spread out out doors will allow the heat to dissipate into the air.

This will not happen with water based stains and coatings as water will not burn. Another good reason to use water based poly and stains when ever possible.

Jules Dominguez
05-13-2005, 9:27 PM
Well, that blows part of my theory out of the water. So, oxygen isn't necessary for the heat-generating part of the sequence, but of course would be necessary for the combustion. The preventive steps would be the same - don't pile the rags to let the heat build up.

Richard Wolf
05-13-2005, 9:43 PM
as water will not burn.

You have never had my first wife's cooking!!