A Close Call – Tyler Reichelt

Article - May 2, 2011

This Safety Week special article is brought to you by MicroJig!

This cautionary tale was was written by community member Tyler Reichelt.

I had a close call today.

I’m relatively new to the craft and have read up on safety as I’ve gone along. I’ve heard a lot of the horror stories about oily rags and such, but I haven’t used many oil finishes to date, so that topic wasn’t at the forefront of my thoughts just yet.

In any case, I am in the finishing stages of building a workbench and am testing out a few different finishes. One of the finishes I was experimenting with was boiled linseed oil. I hadn’t specifically read up on linseed oil, so I wasn’t very concerned with it. After all, it’s an oil derived from a plant. How dangerous could it be?!

Boy was I was wrong! I was experimenting with both linseed oil and tung oil and was testing different mixtures in little Dixie cups. The linseed oil cup was just about full and the tung oil cup was just about gone. I didn’t think anything of it and poured the tung oil into the linseed cup, stacked them, and promptly poured the mixture right into my dedicated sawdust trash can.

Even when I’m not working in the garage, I still frequently have the urge to go out into the garage and just be around my tools; maybe practice my hand-planing. Well, about an hour after pouring out the oil, I had one of these urges, so I went out. I immediately smelled something burning, but the smell was unfamiliar to me. I thought maybe one of my neighbors was burning something, but when I walked out into the driveway, the smell was gone. I walked back into the garage to try to find the source and when I looked in the sawdust can, I saw a small stream of smoke steadily rising from the sawdust; right where I poured the oil. I immediately ran inside and grabbed a big glass of water and poured it all over the spot. It reminded me of putting out a campfire. When you pour water on it, even though it may not look like much on the surface, when the water hits it, you know something hot is down there. The same applied to the sawdust. Upon digging around with a stick, I pulled out a charred blob about the size of a softball. It was down there smoldering for an hour!

If I had left it much longer or if I had used something bigger than a Dixie cup, the computer I’m typing this on might not have been here right now. I had no idea about the oxidizing properties of boiled linseed oil. Boy do I know it now!

As you can see in the picture(s), this was a disaster in the making. Oily paper towels and linseed oil poured right in the sawdust bin. Lesson learned!

Discussion

Steven Gryskiewicz May 2, 2011 8:55 am

Thanks for sharing. However, maybe someone can confirm my suspicion that linseed oil actually falls in the grease category which would make this a class B fire.
Trying to put it out with water could have potentially made it even worse.

Please correct me if I’m wrong.

Reply
- thewoodwhisperer May 2, 2011 9:21 am
  
  Maybe someone with a firefighting background will chime in on this. But the amount of oil is actually quite small. As it starts to cure, it generates a tremendous amount of heat causing the surrounding material to smolder and ignite. So at the very least, the water is wetting the flammable material making it less likely to flare up while also cooling the small bit of oil. So there are definitely better options than just water alone, but I think I would have done the same thing. Hit it with some water and then separate everything out on a concrete floor or in the driveway so it can cure completely.
  
  Reply
Paul Nunya May 2, 2011 8:57 am

Dang glad you caught it before anything else could have happened, My general practice is to lay the rags flat outside on the concrete and place a rock on top of them until the next day when they are all hard and crispy then I just throw them away or burn them in a metal bucket outside on a none windy day, as far as the left over stuff I normally sit it outside on the concrete also in a corner where it wont get kicked over and if it any combustion happened there would be no fuel for it to burn so it would just burn itself out once the content is hard normally over a 24 hour period then I just throw the lump of harden finish away.

Reply
Stephen May 2, 2011 9:33 am

Osha disposal cans close off so that there is little to no oxygen available to burn. I would say get something similar that is metal and has a tight seal and then wet the rags in addition. I may be wrong but I think heat is only generated as the oil evaporates/cures so I think you can place them in the trash after

Reply
Texfire May 2, 2011 10:55 am

In its simplest form fire has to have three things; fuel, heat and an oxidizer. These three components form the ?fire triangle?. All three must be present for there to be combustion. It?s difficult to remove the fuel, so the most common ways to extinguish a fire are by removing the heat source or depriving it of oxygen. Extinguishing agents are ?typed? according to fuels.

In a class B fire, the fuel consists of a flammable liquid like gasoline, paints, thinners, grease and oils. These liquids will burn as long as the other two legs of the triangle are present. The oxidizer is generally, but not always, air. This is why putting a lid on a burning pan of grease is effective in putting it out, deprived of a ready source of oxygen it uses up the available supply and cannot sustain combustion. However the heat source still must be removed or the heated fuel will flash when reintroduced to an environment containing an oxidizer.

Water is effective in removing the heat component. However it is not an ideal extinguishing agent for flammable liquid fires because it can splash the liquid around, exposing more of the heated fuel to the oxidizer, increasing fire spread. An additional hazard with a grease fire, the grease is superheated past the boiling point of water which will convert any water applied instantly to steam, greatly increasing the spread of the burning fuel.

In the original poster’s situation water was an acceptable extinguishing agent because the oil was acting primarily as a heat source instead of a fuel, and had absorbed into the surrounding fuel, which was the sawdust in the trash can. While a flammable liquid was involved the fuel was primarily a class A one. An added consideration is the heat source was a mild one, causing a slow and smoldering fire instead of a rapid free burning one. So reducing the available heat by cooling the fuel worked. That said, covering the material in a air tight container would have also been effective, as would using a dry chemical extinguisher (ABC type extinguisher) to inhibit the chemical reaction that was taking place.

The take away? Finely divided fuels like sawdust will readily burn given the right conditions and should be treated with respect. Chemicals react in predictable ways but require an informed user. Each shop should have a multipurpose ABC extinguisher available near an exit point.

Reply
John F May 2, 2011 11:03 am

Tyler – wow, that was a close call. I actually cringed when I read that you poured the oil into a sawdust can.

I usually hang oily rags up in our basement bulkhead door (I have a basement shop) – not optimal, but it’s pretty well ventilated, and I make sure they are never layered or bunched together and they dry out quickly.

Another good safety tip is to make a fire extinguisher easily available in your shop. Keeping one on the back of a shelf behind a dozen cans of old finish, some small scraps of lumber, and the remnants of the morning’s bagel, probably is not the best location.

Reply
Lori May 2, 2011 11:35 am

Definitely a scary experience. I am ALWAYS paranoid about fires, more than most probably since my home burned down when I was a kid and I was home alone at the time. It’s amazing how fast a home can go up in flames. To this day I am a bit sensitive to this subject. I took a woodworking finish class one semester in college and they had one of those red trash cans for flammable trash. Well..our classroom caught on fire because someone forgot to shut the lid properly after throwing some oily rags into the trash can. So, even if you have the products that promise safety, using them improperly doesn’t guarantee their success. I’ve seen many homes go up in smoke because of this very subject (one in my neighborhood a few years back), I think this is a great subject to learn more about. I’d really like to learn about what to do with the used finish (in the secondary container) after you are finished with the finishing process. I read Paul’s idea on letting it dry in a container outside of the shop…I think I may try this next time. Do you think the hardened finish can ignite after it’s dried after the 24-hours…or is it the curing process that really causes the smoldering? Thanks for bringing this to our attention!!!

Reply
- Texfire May 2, 2011 2:12 pm
  
  Lori, after the oil is cured, it is no longer a heat source, but just another fuel and can be treated as such and can be disposed of like any other hazardous material.
  
  It’s the curing process, where the oil is oxidizing that heat is produced. If the heat is contained to the object, it can reach the ignition temperature of the oil. This can happen when an oil soaked rag is wadded enough to trap the heat from the reaction inside, but exposed to enough oxygen to sustain the combustion. This is the reason why you should either spread out oily rags on a non-combustible surface until dry. Another option is what your class shop had, a container designed to store oily rags which allows air circulation around the container to remove excess heat, but has a top which seals and keeps oxygen away from the reaction.
  
  Reply
HMG May 2, 2011 12:14 pm

I probably would have dumped the garbage onto the driveway, spread it out, and then hit it with water. If the water spreads the fire, then at least it’s on the driveway versus the garage.

I’d rather have a mess than a fire. Thanks for the post.

Reply
VitalBodies May 2, 2011 12:26 pm

I have wondered what do also. What I ended up doing was finding an empty paint can and peeling the paper label off. I cleaned the inside of the can. Now I have a clean, unpainted and unlabeled metal can with a lid that seals. I put any oily rags or old gas filters or other flammable toxics in the can and seal it. I keep the can located where, should it catch fire it would not catch other things on fire – like on a cement floor. I labeled it FLAMMABLE HAZARDOUS WASTE. I am waiting for the next hazardous waste collection day in our local community to be able to dump it. If I had oily rags to reuse I would have another can just for that and I would attach an extra opener to the can. I got the impression an air tight can, that is not flammable was the ideal solution. Comments and suggestions welcome.

Reply
- Beechwood Chip May 3, 2011 4:01 am
  
  I wonder if there’s enough oxygen in the can so that the oil can cure. If not, then you’re just postponing the problem.
  
  Reply
  - VitalBodies May 3, 2011 2:26 pm
    
    OSHA rag cans like these:
    http://www.amazon.com/gp/redir.....ive=390957
    
    …seem like little more than a paint can unless they have a foot lever.
    I would venture to guess that the speed they cure is a factor in creating a fire. So with little oxygen they would cure (if they cure) very slowly. EMPTY EVERY NIGHT is the other big question, empty them where?
    
    Reply
    - VitalBodies May 3, 2011 4:42 pm
      
      I did not mean for my comments to seem authoritarian, but more of an observation. Not sure what the best solution is for the home shop on the oily rag issue, and clearly it is a dangerous issue.
Derek C May 2, 2011 1:20 pm

Sadly, this is almost the same exact way that my grandparents house was lost a couple years ago. Luckily no one was injured, but there was not one item in the entire place that was saved. Even the foundation was destroyed by the intense heat.

Reply
Tyler Reichelt May 2, 2011 3:51 pm

I’ve done a TON of reading up on BLO safety since this happened. I certainly won’t be making that mistake twice! I’ve been neck deep in BLO the last couple days and I’ve double/triple checked every time I’ve left the garage to make sure I haven’t left any oily rags laying anywhere.

Ironically enough, I do have a fire extinguisher in the garage, but I walked right past it to go inside to get the water. By that time, I’d moved the trash can out to the driveway, so I wasn’t overly-concerned about the smoldering progressing into a fire. I’m just glad this lesson didn’t cost me the family/pets/house/tools!

Reply
Claude Stewart May 2, 2011 6:35 pm

Wow, good thing you make regular checks. I always hang my linseed oil rags up to dry over anything I can find. When I’m finishing it is common to see rags all over my shop. Kind of like nylons hanging in the bathroom years ago.

Reply
Jeff May 2, 2011 8:51 pm

I could not agree more with Texfire. I have been in the fire service for just over thirteen years, and what he said is exactly true. Just to add a little tid bit to what he said. Several years back, the fire Triangle was changed (in most textbooks) to a Fire Tetrahedron. The three items that he mentioned (fuel, heat and oxydixor) are still there, but a seperate side was added named chemical reaction. This chemical reasction was added to the previously know Fire Triangle, due to the chemical reaction that takes place in “Spontanious Combustion”. Linseed oil soked rags is the standard TEXTBOOK example of a spontanious combustion chemical reaction. Linseed oil rags are so highly reactive when bundled together, that it produced a change in the foundation of Fire Science. I would encourage everyone to be VERY careful with any oil, especially linseed oil. AND FOR GOD SAKE….KEEP IT AWAY FROM SAW DUST! Any fine dust is flammable just based on it’s mass. This is why a grain silo will explode like a bomb.

You can take coffee creamer and through it into a flame, and watch it ignite. DUST IS DANGEROUS!

Again, Texfire did a great job at addressing the topic. I just thought that I would add to his already made point.

Reply
Jason May 3, 2011 5:27 am

Do all oil based products (stains, polyurethanes, varnishes, etc.) have to same ability to randomly combust like the linseed oil described above?

Reply
- PHILIP TWEEDY May 6, 2011 12:18 am
  
  yes they will almost all burn. what is the safe way to handle any wet rags is to lay them out flat to dry. Treat any and all rags, paper towels, stir sticks, and secondary vessels the same way every time as a mater of habit. or some day its burn baby burn….phil
  
  Reply
Claude Stewart May 3, 2011 12:56 pm

I watched them do the coffee creamer bomb on mythbusters. That was a giant fireball.

Reply
J Piper June 9, 2011 8:47 pm

I rarely use oil finishes so I have a question. When I do use them (usually oil based stains) when I’m done with the rags I string a line in my shop and hang the rags over it. When the rags are dry and hard (a day or two later) toss them in the trash. Is this a safe way to dispose of them?

Reply
- thewoodwhisperer June 9, 2011 10:15 pm
  
  That sounds perfectly fine to me!
  
  Reply
- jHop June 11, 2011 6:46 pm
  
  disclosure: not a trained fire prevention specialist
  
  The only thing I would change, J, is to use clothespins instead of draping the rags over the line. Even an accidental breeze, or whatever, might be too much.
  
  I currently use a set of plastic clothespins, under the assumption that the plastic will melt, thereby dropping the used finishing rag into the laundry tub right below. While it’s not perfect, I haven’t gotten burned (pun intended) yet.
  
  and yes, I do have an extinguisher near the stairs out of the basement. It was actually the second item I purchased this year for my shop. (the third was wood.)
  
  Reply
MattO August 12, 2011 10:36 am

I am a trained Fire Prevention Officer, and it was good to see knowledgable responses to this post by Texfire and others.
It is recommended to treat all oil contaminated items as potential fire risks.
I would just add one more note – oils like linseed as they cure draw moisture out of the materials they are in contact with. So those dried rags are extremely flammable, much more so than a normal piece of cloth.
Even dried rags should be removed from the building each day, and placed in a metal container with lid outside the building until such time as they can be disposed of.

Reply
Alex Borins November 11, 2012 6:40 pm

I have been around a wood shop since I could walk, but only in the past year have I stated to take it seriously. My grandfather is my mentor. I have never used linseed oil, but here’s my grand father’s horror story. His sailing buddy had just bought a mildly used 36′ boat with tons of teek inside and out. My grandfather’s boat also had a lot of teek on it as well. She asked my grandfather what he used to finish and restore the teek. He said, linseed oil. He warned her about the fire risk and told her to always air dry out the rags for a few day, rinse them extremely thoroughly, double bag them and throw them away. She had restored most the the cabin. She came in the evening to do a tiny, tiny bit of work. She barely used any oil, so the left the rag to dry inside the cabin and went home. Disaster struck. The linseed oil combusted and a fire started. The cabin however was sealed airtight, or near enough so. The fire ran out of oxygen and stopped. Soon she came back to set sail and opened up the cabin and then she saw what had happened. She called the insurance and they paid to have the interior rebuilt. She got extremely lucky that she didn’t set the whole marina on fire. Needless to say, that was the last time he used linseed oil on anything

Reply

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A Close Call – Tyler Reichelt

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