Rag fires

Re: Rag fires

John Pappas

>Marv, the main culprit is linseed oil. It is a drying oil and generates heat as it cures. If that heat is not allowed to dissipate, it can combust. Experiment, if you insist, with some rags soaked with linseed oil...place in a closed container and see what happens. You will not call that legend. It has been proven many times. Rags used with linseed oil should be hung out to dry, or placed in a container of water.

Re: Rag fires

Scott in Douglassville, PA

>I believe that's how Ellis lost his shop at one point. Hopefully he'll chime in here.

Not a myth. Some oils heat when curing. If left enclosed, they can generate enough heat to ignite.

Re: Rag fires

walt Q

>maybe not an entirely closed container...you do need some oxygen for combustion..

8 years ago I wiped down the wooden album racks in my shop with a linseed oil based wiping varnish...dead of winter, figured a good time for maintenence...anyway, without thinking much of it I balled up the damp rags and tossed them into a garbage bag which I then tied shut and left on the stage of the store....long story shorter...four hours or so later I smelled smoke....the bag was burning pretty good and I ended up with some pretty bad burns getting it put out..scared the he** out of me

never thought about spontaneous combustion before that...but now whenever I have any rags with solvent..I always lay out to dry before disposal.

walt Q

Re: Rag fires *LINK*

Dave Anderson NH

>Hi Marv, Back about 6 years ago my good friend Dave Emerson of Canterbury NH was at the Sunapee Fair manning his 9 day craft fair booth. One of his employees was working with boiled linseed oil and at the end of the day forgot to put the used rags in the woodstove as was the normal proceedure. Dave and Anne were sitting on the deck having an evening dinner when they heard cracking and smelled smoke. The shop, separated from the house by about 250, feet was on fire. An attempt to call the fire department was unsuccessful since the phone line wires ran from the street to shop to house. The nearest house is about 600 yards away and the volunteer fire department is about 5 miles. When the fire department arrived all they could do was hose down the surrounding area to keep the woods from turning into a forest fire. The fire was spectacular and the next day the Concord Monitor newspaper had an 8" x 10" color photo of 200 foot high flames on the front page. Dave lost everything: tools, machines, lumber, jigs and fixtures, plans, etc.

Yes, spontaneous combustion fires caused by curing drying oils are very real and the results can be horrendous. This event was a wakeup call for all of our NH guild members.

The article with pictures of the shop rebuild is on page 4 of the attached link.


http://www.gnhw.org/docs/oldsaw-200111.pdf

Speaking of Myth Busters....

John in New Mexico

>One of the few episodes I've seen featured some guys doing something with hardening steel by heating and quenching in oil. What they didn't seem to understand, is when the oil gets hot enough - after many quenches, it will combust spontaniously. No problem, use fire extinguisher! Only trouble is it just re-lit as soon as the CO2 cleared, 'cause the oil was still too hot. They went through this about three times before it was out.

Another interesting example of oxidation, ie: combustion - Old underground mines would sometimes start burning - oil lamps, mine timbers, etc. If the rock was very high in sulfide minerals, they would start to oxidize and produce a great deal of heat in the process, starting a self sustaning reaction that was basically impossible to put out without flooding the mine (not always possible). One example of this happening was at Jerome, AZ, IIRC. Amazing even to me that rocks will burn!

Re: Speaking of Myth Busters....

ThomD

>Mythbusters is good fun but not reliable. Anyone see the one where they went about making a wooden canon. The myth included the idea that one could drill out a canon with a forged spoon bit. So Jamie forges one up, gives it a couple of twists, well that myth is busted!!

I don't think saturated rags are the problem, but as someone said, damp ones are. I don't use a lot of rags, but I do worry about burning the block down. I was in the local industrial supply and they have these heavy steel pipe containers that are sold for safe storage of oily rags. Seemed like a good idea until I read the fine print that said they had to be emptied every night.

Re: Rag fires

Kevin French, Antrim, NH

>I used to work for Servpro Cleaners, we were called to a New House that the contrators finishing crew had stained all the woodwork then left the rags in a plastic bucket. They caught fire, burnt a hole in the second floor, and smoke damaged most of the house.

On the up side there was no furniture in the place.

It does happen.

I'm now a converted BLO user

Marv

>I use BLO on a regular basis. I usually use paper towels folded to the size that works best. I then just lay them out on top of a lidded container of handcleaner still folded and let them dry there and discard them later. From the stories you guys are relating it sounds like the problem is when the rags or towels are contained in a closed container where the heat can't escape. In any case, I'll be taking them outside and let them contaminate the atmosphere.

Thanks you guys for your convincing posts.

Marv

Re: Rag fires

Moses Yoder in White Pigeon, MI

>Spontaneuos combustion of oily rags is definitely not a myth. Automotive oil will not self combust; it has no drying agent (I used to wonder about that). A lot of finishes are oil based and also have a drying agent in them, or a solvent that evaporates relatively quickly. As the solvent evaporates it creates heat, I think due to molecular movement; I am not a scientist. If the heat is contained in such a way that it builds up past the point of combustion of the oil it will self combust. So you need several things for the rags to self combust; an oil with a low combustion point, a drying agent, air for the drying agent to evaporate into, and the heat contained in such a way that it will build up. This has not happened to me yet because I am aware of it and simply throw the rags over a jointer fence or anything that resembles a clothes line so the drying agent evaporates without building up much heat. A local home shop had been doing some finishing with rags and spread all the rags over the floor at the end of the day for them to dry. When their son came home later that evening he picked up all the rags and threw them into a garbage can. Sometime during the night they lost their shop.

Outstanding explanation, Moses

Wiley Horne

>Sounds pretty scientific to me. I didn't understand that part about the drying agent before.

Wiley

Re: Speaking of Myth Busters....

James Watriss

>Those red cans do say that they should be emptied every night, this is true. But they work. The idea is that the lid will keep oxygen usage down, so the contents will smolder, but even an open flame will be CONTAINED. I've talked to finishers who have had rag fires, in those cans, and they say there's a very telltale smell when they come in the next morning. The place smells like smoke, and the contents of the can are all sorched and singed, or just ashes.

The idea behind emptying it out every night is that you don't want a can fill of a week or more's solvent soaked rags and fumes all waiting to be lit off by a linseed oil rag or something else. Having a fire is bad enough. Having a fire with a supply of fuel is worse.

That, and the liability issue. I've met people who are dumb enough to think that rag in can is good enough, even if the can is overflowing. If the can can't close, it can't work, and the mfr has to take care of liability issues.

The cans do work, and they are a good idea. An oily rag can was one of the first things I bought for my shop.

Re: Rag fires

Jeff Weaver

>I'm a career firefighter, 23 years and counting. It happens, I've seen it. The risk of losing your home and/or family is very real. Compounding the danger is the fact that the consequences of careless rag disposal is not immediate. It usually takes a few hours to develop a temp high enough to sustain combustion, so often you're gone from the area or asleep when the fire starts, which of course gives it more time to grow.

The good news is, these fires are easily prevented. An airtight metal container works best. I got a "rag can" from Harbor Freight for $20. Has a foot lever on the front to raise the lid, which lowers when you release the lever. Maybe the best $20 I've spent on woodworking. Couldn't sleep at night without it. When the rags are completely dry (I always give them a few days), just add them to the regular trash.

Be safe.

Jeff Weaver

A Televised Demonstration

Steve Elliott

>In 2003 there was a show on the Discovery Channel called Unsolved History: The Great Chicago Fire. As a part of the show they demonstrated spontaneous combustion by putting rags soaked in linseed oil in a bucket and allowing them to stand at room temperature.

The rags ignited after 5 hours and 45 minutes.

Mine fires

Bill Houghton, 1.75" rain, Sebastopol, CA

>It's my understanding that some of the coal mines have had fires going for a decade or more. Of course, this is a rather obvious combustible - it's still an awe-inspiring concept.

Try this experiment...

Charles R. Smith from Victoria

>I had an acquaintance who decided to show his teenaged son that finishing rags were dangerous. He put some into a tupperware-type container and then put the lid on part way, to keep in the heat but allow oxygen access to the rags. He put the container in the middle of his sun-drenched driveway on a warm day. Smoke began pouring out of the container about an hour later. By the way, the driveway was made of gravel -- he wasn't going to risk melting asphalt!

Charles (whose son probably doesn't need to be taught how to start fires!)

Re: Rag fires

Frank House

>Moses,

With respect, I think you have the evaporation bit the wrong way round.

When a liquid evaporates it takes heat from its surroundings (latent heat of vapourisation (UK spelling!)), leaving the rag (or whatever) cooler. Old butter dishes worked this way -- wet rag over the dish to keep contents cool.

I agree with you, however, that the drying agent is a key player.

Frank.

Re: Rag fires

Frank House

>Forgot to say, the drying agent does not "dry" the rag by evaporation, but by promoting an exothermic polymerisation process, the heat yielded by this chemical reaction may be sufficient for ignition in the presence of oxygen, and could be helped by any volatile solvent still hanging around.

Frank

Re: Outstanding explanation, Moses: clarifications

Miles

>Unfortunately, Moses' explanation isn't technically correct, though he does capture the common sense facts that air, and a suitable oil composition, are both required.

Heat is not generated by evaporation of anything.

I am some sort of chemist, and this is how I would explain it:

The drying oils like BLO, Danish, Tung etc have unsaturated, reactive molecules that react with oxygen, which starts the polymerisation process and enables them to form a film. The reaction with oxygen is exothermic - releases heat. The reaction also goes faster if the temperature is higher, so it can 'run away' if the conditions are right.

The role of the drying agent (usually a metal like cobalt, but iron and copper are also powerful accelerators) is to speed up the initial reaction with oxygen.

Air is needed to provide oxygen - not much needed at first, but of course a fire can't continue to burn in a closed container, so that is a good precaution. You'd find your rags go stiff (the oil has 'dried' fully) even in a closed container, I think, as not much oxygen is needed to just polymerise the oil.

The key seems to be that the heat from the reaction, if it results in the rags (oil) getting warmer, causes a substantial acceleration of the oxidation reaction, and hence faster heat production and....poof! A big bundle of rags is a good insulator - the ones in the middle can't lose heat very easily, and they all warm each other. Spreading them out obviously prevents this runaway stage of the process. However, the worst case would be any sort of stove or chimney where air would be drawn through the warming rags, and would enable a really good burn once they ignite.

SO - the common practice is perfectly correct, and common sense is explained by the chemistry - but there are a few extra points that might be worth noting:

1) the air supply makes most difference at the burning stage, unless you were to positively squeeze out almost all the air from your closed container, your rag will still dry and stiffen up.

2) evaporation has nothing much to do with the process - it's all about the escape of heat, and there is usually little evaporable solvent involved unless you have diluted the oil with turpentine - in which case ventilating the rags is even more important.

3) heat flow and air flow are not the same - think about stoves and chimneys, and convection from a source of heat driving airflow as a dangerous combination

4) drying agents greatly accelerate the initial reaction rate and do increase the risk of combustion - AND contamination with iron, rust, copper, and so on can act as very effective drying agents so contamination of rags could be an issue - don't mix metalworking and drying oils (might also spoil your finish)

5) Chemistry shows that light also greatly accelerates oxidation reactions, so putting drying oil in the sun can speed it up - how much depends on the oil. It would be interesting to know if anyone has noticed this in practice... (this is why potato chips in clear bags don't last so long).

One key thing that is hard to specify is how long is long enough to leave the rags before they stop being able to self-ignite. The answer will vary so much for different oils, ambient temperatures, and drying agents that no one answer could be right. However, once the rags have gone stiff, it's probably a fair bet that they have done most of the oxidation (though they will keep on slowly hardening for a long time). It may be that the smell could tell you something, but I don't know if that would work in practice. Staying on the safe side and taking positive precautions is going to remain the only good bet.

I hope this helps to explain some of what most people already know, and if anyone wants more detail on how oils oxidise, I have plenty of technical material that goes into detail - it's actually an extremely complex bit of chemistry, and the paint, varnish, and food oil industries have studied it for the last hundred and fifty years without figuring out all the mechanisms. However, we do know why BLO smells that way and that you can't make good-tasting oily food that lasts a long time!

Miles

Not just rags...

Rob Lee

>... you also have to be careful with chips and scrapings.

We coat our warehouse floors with tung oil (a great concrete finish!). Sometimes though, it gets overapplied, and the finish will flake. if the flakes are swept into a pile, they can spontaneously combust... happened here!

You have to be careful with anything that oxidizes, and any process which increases the available surface area for combustion, while at the same time allowing heat to build (which is what happens when you pile flakes, or ball a wet rag).

Cheers -

Rob

thank you Miles!

Mike Schwing from Md.

>Thank you Miles. You may have just saved my house. I have always thought that if I contained the rags in a small plastic container that there would not be enough oxygen present to cause the reaction. Looks like that was dead wrong. For years I have been doing one of two things - if I was to use the same sponge/cloth again the next morning I put it in a plastic baggie and closed it. Or, I would hold the sponge in my hand and remove my disposable rubber gloves around it, so two rubber gloves sealed off the sponge, and then took them outside and set them on the flagstone until I could deal with them more properly.

Guess I have some new procedures to put in motion.

Re: Rag fires

Tony Augruso

>Happened to the new house being built on our street. The painters were staining/finishing with oils. Someone left a pile of rags in the middle of the garage floor. When my wife and I were out for a walk that evening, I noticed a glow coming from the garage window. I went and took a look in and saw a fire.

Called the fire department and they put it out.

It will happen if you use drying oils and don't properly dry/dispose of the rags. I spread mine outside on gravel so that they are not even in the house.

Tony

Re: Rag fires

Marv

>Many thanks to all of you for your responses.

Bottom line.....take it outside, leave it outside. Next year sometime, dispose of your rags legally. This will prevent a fire....But....

But this raises another question.....At some point, the airborne type chemicals will disperse into the atmosphere. Are we as woodworkers contributing significantly to what is being referred to as "Global Warming"?

Are our used rags ending up in our landfills?

Marv

if you want to go there

Mike Schwing from Md.

>Be careful where you tread. After all, our hobby depends on cutting down trees, just for starters.. I would think oil rags are the least of our "green" issues. (which cause me no concern, btw)

Re: if you want to go there

Pam Niedermayer - Austin, TX

>Assuming the area of cut trees is replanted, it may actually benefit the air as faster growing trees actually take up more CO2 than the slower growing, older trees.

Pam