Woodworking Safety Guide

How to Safely (and not so safely) Dispose of Oil-Soaked Rags

comments (21) May 8th, 2009 in blogs, videos

MBerger Matt Berger, contributor
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Video Length: 2:03
Produced by: KiwiPeteACT via YouTube

QUESTION: The safety quiz on FineWoodworking.com says to put oil/finish soaked rags in a covered metal container. Isn't it better to allow the volatiles to evaporate in a well-ventilated area first, so as to avoid spontaneous combustion or explosion? - via Knots

For those of you who are unaware of the safety hazards associated with oily rags in the shop, news reports about shop fires started by improperly stored oil-soaked rags are common place. And it's always the same story, a wadded up oily rag combusts and leads to a total-devistation fire (as seen in the YouTube video above and described in detail in Chris Minick's article in Fine Woodworking issue #177.)

Safe home-shop solutions
As many astute readers pointed out in the Knots forum, the answer we provide in the quiz of storing your oil-soaked rags in an airtight metal container (like this one) only works if you subscribe to a service that collects those oily rags for proper disposal.

"Unless proper removal and disposition facilities are available, you have just post-poned the problem," writes Steve Schoene in the Knots forum. "The OSHA regulation that talks about this 29 CFR 1926.252(e) clearly means this as a temporary measure 'until removed from worksite.'" 

Our recommended solution pretty much exludes the common home woodworking enthusiast who would find a rag-collection service an unrealistic option. So what's the alternative?

"The final solution," Steve writes, "requires either destruction by something like burning, or a safe way to let the material cure without cumulating heat.  For home and small commercial shops, the easiest way is to spread the rags in a single layer so heat dissipates while the material cures. Then, depending on local regulations, the materials can be safely disposed of, either in hazardous waste collection sites, or in the general landfill." 

UPDATE: To answer the comment below, an oily rag has cured when it becomes hard and brittle. The time it takes to cure can vary considerably depending on humidity, temperature, and the finish.

Mike Hennessy is one of several who follow a similar solution: "I usually lay my old rags out flat on the ground outside to dry. That way, not enough heat can build up." Another reader replied that he incinerates them in the wood stove.

I have to admit, while I helped write our new safety quizzes using our library of expert texts as resources, I typically dispose of my oily rags by hanging them over the edge of a trash can until they dry, and then throw them in the trash. Time to go write a new quiz question, I guess.

posted in: blogs, videos, fire safety

Comments (21)

CRHarman CRHarman writes: In order for spontaneous combustion to occur, it needs three elements; vapors/gas, oxygen, and heat. If one is missing from the equation, combustion cannot occur. I simply place my HAZMAT in a sealable metal container filled halfway with water. This dilutes the chemicals but will still give off vapors. Keep away from direct sunlight or other heat sources. Check with your city to find out how to correctly dispose of your household HAZMAT. DO NOT directly rinse chemical soaked rags into the drain system. Many city street drain systems are unequipped to properly strip and dispose of HAZMAT. Additionally, the EPA (Environmental Protection Agency) provides hefty fines for illegally dumping HAZMAT, ranging from 5,000 to 5 million or up to 7 years in prison. If you burn your rags keep in mind that you are inhaling toxic fumes which can cause health risks. When referencing your product MSDS soon to be SDS, review how to maintain and at which point the chemical compound is self combustible. Treat the use of chemicals as you would the operation of dangerous machinery.

Semper Fi
Posted: 2:02 pm on February 11th

DecibelGuitars DecibelGuitars writes: I keep a folding clothes drying rack and/or a retractable clothesline in the shop for drying oily rags.

Keep it along the wall in an out-of-the-way place, or even mount the clothesline to make use of unused space under a workbench!

String it up while cleaning up the shop for the day, and the rags will usually be dry by morning.
Posted: 12:20 am on December 14th

Sario Sario writes: Luckily, my shop is heated with a wood-burning stove. I get rid of oil-soaked rags by just chucking them in the stove. If they don't spontaneously combust, they sure will the next time I start a fire in the stove.
Posted: 6:57 pm on May 18th

breezyridge breezyridge writes: What are the ramifications of rinsing the oil-soaked rags and sending the water down the drain? Is it OK to send that material to the water treatment plant? If the oily water goes down the storm sewer, would it go to the local waterways completely untreated? Would dumping the water into the back yard send it into our ground water? Would burning the rags send the smoke and fumes into the air that we breath? Maybe the best way to dispose of it is to let the rags dry and send them to the land fill where the contaminate is somewhat contained, at least in theory.
Posted: 2:56 pm on May 14th

DRR DRR writes: I have also burned down a couple of dumpsters. Having worked for 30 years of production woodworking and finishing, I found that the safest way to dispose of large quantities of oil-stain rags was to soak in water. I continue to use this method in the co-op hobby shop.
Posted: 8:11 pm on May 13th

BillAltemus BillAltemus writes: I use small strips of cloth for the oil application. To despose of them I rinse them first. I use two different size metal buckets one inside the other to dry them. I drape the rinsed strips over the lip of the inside bucket. The strips are short enough that they don't reach the bottom of either bucket. In a few days when they are dry I put them in the next outgoing trash bag at the time I am putting the bag out. I've followed this procedure for over thirty years after reading of fires started by problems with desposing of these types of rags. I don't like to trust covered metal cans as recommended on so many of the product can labels.


Posted: 8:01 pm on May 13th

bcbwc bcbwc writes: I made the mistake of draping linseed-soaked rags over a wheelbarrow's handles once. Came out to the garage to find the handles and rags smoldering. Won't do that again!
Posted: 7:05 pm on May 13th

DerekH DerekH writes: One thing not mentioned is that there are oily rag cans for such a purpose. They are heavy metal and the bottom is raising up and holes punched through the sides (beneath the bottom), so that temperatures don't get too high on the floor. They are foot operated and the lid closes automatically based on it's weight.
Posted: 5:37 pm on May 13th

quattro4 quattro4 writes: When I'm done with tung oil, linseed oil rags,etc, I always put them in a bucket of water outside my back door. I let them soak overnite then dispose of them in the landfill. This way I'm assured that it is made non-combustable.

Posted: 1:46 pm on May 13th

Bidgybudget Bidgybudget writes: Thanks for a reminder of this often forgotten hazard of the shop. Oily rags and other fire hazards are so easy to forget in the rush to clean up at the end of a day.

The fact is this article should remind us to review ALL our shops for fire hazards and fire protection systems. A wood shop is full of combustables, saw dust and solvents just to start.

So... Can you kill power to the shop from outside the shop?How are you fire extinguishers? DO you have enough so they are where you might need them? of the right kinds? Have you checked them lately to be sure they are charged? A fire extinguisher buried under a heap of stuff or one full of powder but no propellent is not much use when you come back from lunch to find a smoldering fire in the dust collector.

Polyester resins are another source of shop fire hazards. The amount of hardener determines the rate of cure and the cure is exothermic, that is it gives off heat. Too much hardener or too large a batch of mixed resin/hardener can become a toxic smoke bomb in minutes and a serious fire in not much more time.

Remember the old fire triangle when deciding what to do with rags and other hazards. To have a fire you need three things: fuel, oxygen and heat. In the case of rags the best bet is to avoid heat build up since the fuel is in the rags and the oxygen is, well, everywhere. An airtight can is fine for short term storage but eventually the rags have to come out in the air. Allowing air drying in a way that avoids heat build up is really the only practicle solution. I doubt my neighbors like the display but the chainlink fence out back (As TonyCz mentions above)is a perfect place to dry out rags. The garden hose is right nearby if things get uppety.

For the dust collector and trash can, the best solution is to get the fuel out of the shop to avoid fires. That means religously emptying them daily no matter how little you sawed that day.
Posted: 1:20 pm on May 13th

Uponthesquare Uponthesquare writes: Just a little correction to a blog by Chris (14:38:00 May 12th)

The MSDS provides lots of good info. Chris mentions some things it includes. They include the flash point. The flash point is not quite as he describes. [I am a chemist, have measured flash points, and thus am qualified to answer this concern.] The flash point is NOT the temperature that spontaneous combustion will occur. It is the temperature at which a fuel/air mixture will ignite when exposed to a small ignition source (usually a flame about 2mm diameter) for a specified period of seconds in a closed container.(about 2-5, as I recall) The test will return variable results, depending upon which type apparatus is used. For most fluids woodworkers use, this probably should be a "Tag closed tester" which measures flash points that are typically pretty low... on the order of 140 F or less. Actually, if it is a well-made and thorough MSDS the type apparatus used will be stated. However, they often aren't so thorough. This is bad, because the measured flash point will vary depending on the type device used to measure it.

The temperature that a material will spontaneously burst into flame is defined as the "autoignition temperature" which is similar to the flash point in how it is done, but there is NO external ignition source provided. This is in my experience always somewhat higher temperature than the flash point. However, the point is moot. The key learning is that materials with a low flash point are more easily ignited than those with high flash point. The other learning is that if you measure the RATE that temperature rises in those oily rags, for example, you will find that as time goes by the temperature climbs ever faster until it ignites. This means that there may be only a very short time between the time an oily rag reaches the flash point of the (let's say linseed oil) and the time it gets to the autoignition temperature. Also the more quantity of (linseed oil) you have the faster the rags will get to the burn point. But a very good blog point.

Sam Whitley
Analytical Chemist
Posted: 11:20 am on May 13th

TonyCz TonyCz writes: I find this post very interesting as many folks I talk to really don't understand what spontaneous combustion really is and how dangerous it can be. Years ago I was working on a addition remodel and a painter on the job had left oil / staining rags on the concrete floor in the garage off the new kitchen. Wala! he burned down the garage. I always set all oil soaked rags on a chain link fence to dry like laundry and never placing one over the other. I just spread them out and the next day they are dry and ready for the garbage can.

Also fresh cut grass can do the same left in a pile and over just one to two days in the summer can start on fire as well. Composting can be a fire danger as well.
Posted: 10:51 am on May 13th

BobNickey BobNickey writes: I place my oily rags in water. This should keep them cool and prevent compustion. Any Comments
Posted: 10:48 am on May 13th

BryanBrown BryanBrown writes: Keep in mind a bit of cotton wool or rags soaked with some boiled linseed oil was one of the BOMBs the OSS used to teach the Resistance to use to burn down Nazi facilities. In today's military manuals it comes under Improvised Explosive Incendiary.

I am in the hang single file on the edge of a metal trashcan camp for disposal, when they are stiff I chuck them into the can for disposal. Either to the dump or the burn pile depending on season. (We can legally burn yard waste and general non construction refuse here in SC) I have a old ammo can I use for transporting rags back from a project if I am not at my shop and can be certain of proper disposal.

My buddy hangs his on an aluminum ladder out on the porch of his shop.

I have been know to use them to start the burn on my brush pile.
Posted: 10:15 am on May 13th

RLWJr RLWJr writes: One thing that needs underlining is that spontaneous combustion does NOT mean just that they are easily ignited!
I remember lots of posts on the old UNIX newsgroup rec.woodworking where it became clear that people thought all they had to do was to keep the oily rags away from fire.

The point is that the oxidising reactions that are the heart of many oil finishes curing are the same as very slow burning, and that if heat cannot get away fast enough the temperature will build to the point of bursting into flame, with no external ignition required. I have almost had this happen: I left some rags for just a couple of hours for a project I was going to get back to, and when I did get back they were beginning to smoke and were so hot I could not touch them. And I have seen a dumpster at a home construction site burst into a really big fire: They dumped in sanding dust from new floor, then some sort of oil on top of it. The flames shot 30 feet out of the top of the dumpster...

Bob Wilson

Posted: 9:31 am on May 13th

blackemmons blackemmons writes:
I would say that the little bit of smoke a paper towel or two produces on occasion is much less than what my neighbor produces mowing his lawn or my house would, going up in smoke.

I could produce emissions if I took up smoking.

But, I do appreciate the advise.
Posted: 9:28 am on May 13th

dlbrass dlbrass writes: A post or two suggests burning the oily rags and waste. I suggest looking at your local laws regarding this, I know it is illegal to burn this waste around here and I suspect similar laws exist in most areas. Your local fire department should be able to answer this kind of question for you.

In order to avoid this problem as much as possible, I use water-based products when I can. There are differences that take some adjustment, but water-based products are easier to clean up and much safer overall.
Posted: 7:54 am on May 13th

matt_ww matt_ww writes: This indeed is helpful info, but how long does it typically take for an oil-soaked rag to "cure" - hours, days? How can one tell when it's finally safe to dispose of the rag?

Posted: 7:12 am on May 13th

meh725 meh725 writes: Hear, hear!

Some time ago I stripped and oiled a customer's cedar door. Running late and being in a rush to get home, I stuffed all the oily waste into a plastic bag which I just tossed onto the passenger seat of my truck.

Arriving at home just fifteen or so minutes later, I grabbed hold of the bag without thinking, to dispose of it properly, and burnt my hand badly, so intense was the heat.

I can only imagine that only a few moments delay could have easily resulted in a moving vehicle fire.

I learned a good lesson that day and was pretty lucky to have avoided a severe penalty for my lapse.

Posted: 3:04 am on May 13th

blackemmons blackemmons writes: For forty years I've kept it safe and simple.

I have a metal pail outside the shop and I burn anything that comes in contact with flammables(solvent, varnish, wax, whatever) immediately. That means rags, brushes, Q-Tips, stir sticks, etc.

Just put it in the pail(small amounts at a time) and use the butane grill lighter.

Posted: 6:15 pm on May 12th

cptully cptully writes: First, as demonstrated in the video, NEVER drape an oily rag over a plastic or wooden object, as they may well reach combustion temperature BEFORE the rag!

I was lucky enough to find an unused solvent disposal trash can (heavy gauge metal with a tight fitting foot operated lid) that I use for all such waste. Since my production of such waste is relatively small, the solvents and oils usually dry and/or solidify long before it is full.

Keep in mind the flash point of your solvent or oil (should be on the can or the MSDS for the product) when deciding where to dry a soaked rag. In most cases where heating is a problem, a shady spot is to be preferred over a sunny spot to avoid the aggravation of solar heating added to the oil's heat of polymerization.

For those who do not recognize MSDS, this stands for Material Safety Data Sheet, and is a typically four page document that details the hazards associated with a product and protective gear or measured required when using it. The MSDS will include a lot of info that is meaningless to the average woodworker, but it will also include data such as the Flash Point (the temperature at which a material will spontaneously burst into flame). By law, the MSDS is freely available. The retailer may or may not have one, but the manufacturer's website or technical support line should have one that can be downloaded, faxed or emailed.

Posted: 2:38 pm on May 12th

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Woodworking is a solitary hobby and it requires tools and techniques that are inherently dangerous. These two factors make workshop safety a top concern for any woodworker. When working in the shop it is important to protect your eyes, ears, and lungs, and take great care when using hand and power tools. These safety manuals prepared by the editors of Fine Woodworking provide the foundation of safety knowlege every woodworker should know.