Spontaneous Combustion

[Dean Egnater]

Have to admit I always thought spontaneous combustion was an urban myth (except in the case of the drummer from Spinal Tap)

But I always followed the rules anyways....pic attached is what if found left over of an old paint can with some oil soaked rags on it....set it on the shelf of my bbq to dry out. Note the gallon can was not squished down when I put it there.

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[Steve Rozmiarek]

Scary stuff! The town grocery store burned when I was young for the same reason. How many rags were there?

[Aiden Pettengill]

Nothing to do with oil but when we mix epoxy to fill the crack where two counters meet at work and leave it in the cup, it will start to smoke so I guess its possible that it could catch on fire if you weren't careful.

[Frederick Skelly]

Very. Scary. Thanks for the reminder. Glad you are safe and your home is ok.

[Mike Burke]

My brother in laws wife and kids stained their deck and threw all their rags in a pile and left them on the deck. They awoke to a fire on their deck. Lucky they caught it early enough to get it put out them self's. Could have burnt the house down. They didn't even think about the combustion part.
I have never had it happen to me but always lay rags out flat on concrete after using. It does happen...

[Alan Lightstone]

I bought a Oily waste garbage can, or whatever they call them, and wet the rags. But, wow.

FWIW, when using epoxy, I put the cup with the leftover epoxy in another plastic container with an inch or two of water in the bottom.

Again, impressive picture. Thankfully, nothing burned down.

[Eric Arnsdorff]

I understand this can happen with various items that produce heat during cure (exothermic reaction for the full nerd term).
However, I'm curious what specifically this paint/oil was. I expect it was a very common finish.

[Alan Lightstone]

I understand this can happen with various items that produce heat during cure (exothermic reaction for the full nerd term).
However, I'm curious what specifically this paint/oil was. I expect it was a very common finish.

It's obvious - just read the label on the can. :eek: :D

[Mike Kreinhop]

It's a good think the can was outside! Here's a video from Atomic Ryan showing his experience with boiled linseed oil.


https://www.youtube.com/watch?v=v0CPhmplHek

[glenn bradley]

By putting oily rags in a can you created the de-facto test setup used to demonstrate this dangerous practice. Lay the rags out flat to dry, then throw in the trash. I am glad folks post these things since despite numerous warnings on forums and being mentioned in almost any book on workshops these fires keep happening.

The same goes for extension cord reels whether spring loaded or not.

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We keep seeing folks load the cord without unreeling it and having a meltdown. If it wasn't so dangerous it would be funny. Let's all be careful out there.

[Al Weber]

My OCD mentality after seeing this happen in a high school wood shop class years ago causes me to immerse any finish soaked applicator including foam brushes in water in an old Tupperware container and put it outside on a non combustible surface. Probably overkill but better than a fire especially in a shop filled with dust and wood.

[Bill Carey]

As I'm working I'll put the rags in a bucket of water, and at the end of the day I dump the bucket full of rags and brushes on the fire pit out back. Never had any fires but it only takes once - not worth the risk.

Glen - somehow I didn't know that about cord reels. Must have been my sheltered childhood. Thanks for bringing it up.

[Bob Riefer]

Wait, what about cord reels? I haven't heard that one before, please tell

[Micah Puscheck]

Wait, what about cord reels? I haven't heard that one before, please tell

I hadn't heard that either (though I don't use reels), but I could infer that if you had a long extension cord on a reel and were using a significant draw over a long period of time that the heat from the center (of the corded area) of the reel would not be able to radiate it's heat away. It would just sink into the surrounding cords. Do this for long enough with a thick enough reel and you might eventually cause a fire?

[Mike Kreinhop]

Wait, what about cord reels? I haven't heard that one before, please tell

The instructions that came with my Dirt Devil vacuum cleaner, with retractable power cord, stated the cord must be pulled out to the yellow marker before using. The reason given was excessive heat in the cable during use would build up if the cable was only pulled partially out and could be a fire hazard.

I noticed one of my 25-meter extension cords was hot after about 20 minutes of continuous use with my shop vac when I had pulled out about two meters of cable from the reel. When I pulled all of the cable off the reel, the cable didn't even get warm for the rest of the day of similar use.

[Bob Riefer]

Wow, good info. I use a ceiling mounted reel for connecting to my router and sander all the time, and will need to check into whether it's an issue... I like only having a little bit of cord out when only a little bit is needed, but I also like being a fire-free space.

Also, to the OP, glad things ended up ok in your case. Scary stuff and a great reminder. I too use the "lay out flat on concrete" method as that was how I was taught during woodworking class many years ago.

[Brian Tymchak]

Wait, what about cord reels? I haven't heard that one before, please tell

New info for me too. I don't use a reel either but good to have the awareness. Never considered the possibility. Thanks for posting Glenn!

[Dean Egnater]

Scary stuff! The town grocery store burned when I was young for the same reason. How many rags were there?

Only 2....and not very big

[Dean Egnater]

I was Ipe deck oil.

[Dean Egnater]

They weren't in the can...the were on the can (to keep the finish off the BBQ) Though admittedly they weren't laid out

[Richard Coers]

The cord reel is really similar to running wire in conduit. You need a certain amount of open area in the conduit so heat doesn't build up. Cord reels can also have electrical contact issues. If you pull too many amps, the copper contact wipers can arc and burn out. Hopefully the sparks won't land in sawdust.
A salesman at the local tool and wood store had a total loss of his shop. He used danish oil finish and put the rags in a plastic garbage can. When he came out after supper, the whole shed was ablaze. The can started to burn, and since it was sitting next to his John Deere lawn tractor, the plastic gas can on it melted and caught fire also. From there the fire built at an incredible rate.

[Rick Potter]

One point to add.

The can you put rags in should be metal, not plastic.

Note OP's original pic.

[Austin Grote]

The electrical cord reels that I own have a warning label on them to always fully extend the cord when in use, they are at least 20 years old.

[Ken Combs]

The electrical cord reels that I own have a warning label on them to always fully extend the cord when in use, they are at least 20 years old.

JMHO, but that warning is only needed if you load the wire to its limit, or nearly so. Heat will not be generated in any appreciable amount when drawing 4-5 amps for a sander through a 14ga wire for instance. But if you have one of the cheap 16 gauge cord reels and use a 15a saw on it for a long time, it will heat.

Also, JMHO, but the vacuum makers that 'undercord' their vacuums should just put the right cord on it,nota warning label.

[Roger Feeley]

Has anyone deliberately tried to get rags to combust. I might want to demonstrate it sometime. I would like to set up something that would combust within an hour or two.

[Dan Friedrichs]

So what is the best practice with oily rags? I thought a closed metal can was correct, but according to the OP's picture, no?

[Wes Grass]

I thought I had a report saved on spontaneous combustion, but can't find it. Or online. It was based on mineral oils (which don't) but had some data on 'drying' vegetable oils as well.

They oiled rags or paper towels and wadded them up inside others for insulation with thermo-couples inside to measure temperature rise. Some had a measurable rise, some (mineral oils) had basically none. I think Linseed was already in combustion mode before their test period was over. For all practical purposes, it was the only one, from what I remember.

So it seems a fairly simple test. Paper towels would light up easier, I'd think. Probably need to experiment how much to soak them, and how much to wrap them up.

I heard a story about someone staining a fence and coming home and it had caught fire. Stories like this usually involve a neighbor kid who 'saw the fire start' and called the fire department. Which translates in my mind to: 'He smelled the solvent and wanted to see if it would burn".

Kid up by my place blamed it on some horseback riders throwing a molotov cocktail in the bushes. Firemen were like 'umm, yeah ... ok. If you see them again give us a call'.

[Pete Costa]

A year or so ago I was woken up at 1 in the morning by a very nice police officer who asked if that was my garbage can on fire out on the street. It was, in fact, my garbage can. I'd used BLO to finish a project a few weeks earlier and, knowing how dangerous those oily rags were, I spread them out over branches outside my shop to dry out. After what seemed like a very safe amount of time, I threw them in my garbage can, which then caught fire about six hours later. All I can figure is that it had been raining off and on while the rags were on the branches, so they must not have fully cured. Thankfully it was garbage day, otherwise the can would have been in my garage.

As for extension cords, I used to work at a fire protection engineering firm where we had a display wall of cords that had caught fire, sometimes with really bad results. The cheap ones with three sockets on the end seemed to be the worst. They are often overloaded and get scrunched up behind a sofa or something to get them out of sight. Don't do this!!!

[Jim Matthews]

So what is the best practice with oily rags? I thought a closed metal can was correct, but according to the OP's picture, no?

Submerged in water, if in a container.

Spread out to dry in a shaded patch of grass - away from structures you don't want burnt down.

[Rick Potter]

When I looked at the original pic, I assumed it was a plastic one gallon paint can. The metal lid was not damaged.

Let's ask the OP. Dean, was that paint can one of the newer plastic ones, or was it metal??

[Tony Latham]

I looked on the MDS sheet for this stuff wondering if it had linseed oil in it. Which it doesn't reveal.

I've been told that linseed is the underlying substance with this problem. Anyone?

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[Rick Potter]

Natural oils like Linseed, Teak, etc. are the culprit. Dead Dinosaurs are not involved unless you have an ignition source.

[Bill Dufour]

The cord reel thing is not just resistance heating. It can function as an inductive heater with or without a metal core. Welders have known this for decades, ever since ac was invented. It is not an issue with DC. This is a similar reason that spark plug wires are not in nice parallel symmetrical runs
My Mom had a good story about the night before huge concrete pour they realized they had to electrically insulate all the rebar connections for the foundation of a particle accelerator since it would use pulsed magnetic fields. Otherwise the rebar would form a current loop and soak up energy like an induction stove.
Bill D

[David L Morse]

The cord reel thing is not just resistance heating. It can function as an inductive heater with or without a metal core.

No, that's a common internet myth. An extension cord has two wires with equal and opposite currents. The magnetic fields cancel. That's why you have to separate the two wires to get a reading with a clamp type ammeter.

There is common mode inductance of course, so if you have a ground fault, yes, you get some field, but not in normal operation.

[Bill Dufour]

Now you will tell me crosstalk on phone wires is a myth a swell.
Bill D

[David L Morse]

Now you will tell me crosstalk on phone wires is a myth a swell.
Bill D

No, just a different cause. Twisted pairs are use to reduce crosstalk, but you don't get complete cancellation in the nearfield. And that's the last of it. No further derailment of a good thread.

[Dean Egnater]

My rags were on top of the can...not in it

[Dean Egnater]

Paint can was metal...but rags were on top of the can not in it. Burned hot enough to crumple the can.

[Larry Edgerton]

When I first started using epoxy I mixed a batch in a soup can on a hot humid day. When I picked up the can in a couple of minutes it burnt my hand pretty bad. Without mistakes there is no learning, but I would much rater learn from yours!:D

[Paul Haus]

I've never had spontaneous combustion happen to me but then again I'm a bit anal on it. I grew up on a farm and I've seen a couple of barns burn down due to spontaneous combustion. I have a rack and water jug I put outside to dry out any oil impregnated rags I have used.

[Warren Lake]

trimmed the rose of sharon at my families, several hours later moved the bag of trimmings and it was hot, didnt have the digital meter with me. I know grass clippings heat up a little but this was hot and when I opened up the bag there was smoke coming from them. Dont know if it has anything to do with how fast they grow but those suckers are on steroids. I will never leave a bag of those in a garage.

[Michael Rector]

Linseed oil oxidizes as it dries out, that oxidation is what causes the exothermic reaction.

The chemistry behind it is pretty awesome and because it’s an oxidation reaction, robbing it of oxygen prevents it (submerge in water, tight can lid).

[Wes Grass]

There's a paper on it if you search for 'low temperature oxidation of linseed oil'. I scanned it rather quickly. It's over my head to really read and comprehend it.

Things I didn't know:

It's the metallic compounds added to speed the drying that are responsible.

It gets heavier as it dries, from the oxygen it absorbs.

It's used in the manufacture of 'Linoleum'. Never really thought about where that name came from.

[Tom Bender]

Hazmat day next week, guess that can of linseed oil goes. I never use it anyway and a leaky can could be disastrous.