Auto ignition of oily rags

[mbond]

FYI as a warning to others, I just had an incident of auto-initiation of oily rags. A contractor I hired was staining some cedar, and threw all of the stuff into the dumpster. a couple of hours later, there was a giant smoke plume and the whole thing was on fire - a significant event in the city.

My garden hose was enough to fix it in less than 10 minutes, but it is a good reminder about the need to handle these materials with some respect

 

[YotaBota]

You would think a contractor "should" know better.

 

[trlvn]

I strongly suspect that the garage fire next door to us was due to spontaneous combustion of oily rags. The new neighbours were having flooring installed and finished before they moved in and the fire started about 2 hours after the flooring crew knocked off for the day. The garage went up like a Roman candle and they were fortunate that there was 'only' smoke damage to the rest of the house.

Craig
(My wife called in the alarm.)

 

[Tom O]

That’s something that I find surprising we were told that the first year of woodworking in school back in the mid 60’s but what I find interesting is Princess A, H Depot, or Canadian tire don’t stock anything like that. I’m planning to buy a stainless kitchen garbage can and plate the bottom of it.

 

[Doggggboy]

Bourbon Moth did a video on this.

 

[Elektrishun]

Reminds me of a local house that burned down about 4 years ago. Apparent source was a linseed oil soaked rag used for staining a deck left in the sun on an exceptionally hot summer day.

Link to story:
Spontaneous combustion of oily rag

 

[skippyelwell]

Reminds me of a local house that burned down about 4 years ago. Apparent source was a linseed oil soaked rag used for staining a deck left in the sun on an exceptionally hot summer day.

Link to story:
Spontaneous combustion of oily rag

I was just about to say that linseed oil and other plant based oils are usually the culprit, petroleum oil soaked rags don't oxidize so don't burst into flames like other oils. If they did my shop would have burned down decades ago.

Like @Tom O , in woodworking class in high school a fire fighter came to our class one day to talk about the subject so what I just said above is 50 yr old intel, take for what it's worth.

 

[DPittman]

Like @Tom O , in woodworking class in high school a fire fighter came to our class one day to talk about the subject so what I just said above is 50 yr old intel, take for what it's worth.

We had a really good demonstration at our high school shop about 35-50 years ago also ....it burnt down due to linseed oily rags left overnight. Well it actually didn't burn down all the way but did serious damage.
While I am still careful with petroleum oily rags, I am also doubtful that they will spontaneously combust like linseed oil rags. I do remember our shop teacher trying to demonstrate linseed oily rags spontaneously combust by placing them in a metal garbage can overnight and nothing happened. I believe just the right conditions need to exist for that to happen.

 

[trlvn]

Apparent source was a linseed oil soaked rag used for staining a deck left in the sun on an exceptionally hot summer day.

Just to be clear, neither sun nor ambient heat are required for spontaneous combustion. As linseed oil cures, the process creates heat; quite a bit of it. If the rag is wadded up, there will be several surfaces concentrating the heat and the temperature may climb to the ignition point for the material.

One way to safely dispose of such rags is to lay them out flat until the linseed oil dries/hardens. The curing process still creates heat but it won't be concentrated enough to ignite. 'Tung oil', 'Danish oil' and others have the same potential problem. The container will indicate a flame hazard if it is susceptible.

When I was a kid, there would be a barn fire every year or two. Hay that is not sufficiently dry can spontaneously combust. (I don't know the details of the heat-producing reaction. Surely one of our engineer/farmer-types will!) All the farmers I knew were very cautious about the hay being sufficiently dry before going into the mow. I guess large bales used now are safer?

Craig

 

[Doggggboy]

When I was a kid, there would be a barn fire every year or two. Hay that is not sufficiently dry can spontaneously combust. (I don't know the details of the heat-producing reaction. Surely one of our engineer/farmer-types will!) All the farmers I knew were very cautious about the hay being sufficiently dry before going into the mow. I guess large bales used now are safer?

I believe the heat is generated through what is essentially composting. When I was a kid on the farm we would put up thousands of small square bales of hay each year. Tame hay in July and ditch hay and slough hay later in the early fall. We never really had the luxury of waiting until everything was the perfect dryness. You baled it when you had time. If the hay was wet we would either tumble stack it with the elevator to improve air flow or hand stack it and salt between the layers. A friend had a commercial hay farm and had a large drying shed where all the hay was stored. There was a central tunnel with huge fans at each end. The floor was slotted and when the fans ran the air was forced down the tunnel and up through the floor to dry the hay. We fed our hay to the cows. He sold his to the horse people, (they're crazy) and even 40 years ago they would pay 2-3$ per bale for a 40lb square.

 

[Susquatch]

Surely one of our engineer/farmer-types will!)

Aimed at me?

All the farmers I knew were very cautious about the hay being sufficiently dry before going into the mow. I guess large bales used now are safer?

Yes, but large bales are actually more susceptible than small ones.

Wet hay + microbial activity + insulation = heat buildup. If unchecked, this heat can eventually cause the hay to ignite on its own.

It's the same as plant oil on rags except in the case of plant oils its the oil curing that produces heat and with hay and compost its the microbial action. In both cases, the solution is to spread things out to reduce insulation factor to prevent heat accumulation. In the case of hay, don't bale wet hay.

Most farmers know that wet hay causes mold and can also self ignite. Sometimes, they push the envelope and pay for it.

 

[Susquatch]

trying to demonstrate linseed oily rags spontaneously combust by placing them in a metal garbage can overnight

No oxygen left to support combustion or wrong oil chemistry to reduce curing rate.

 

[DPittman]

I guess large bales used now are safer?

Nope still happens if hay is put up wet.

 

[Elektrishun]

Just to be clear, neither sun nor ambient heat are required for spontaneous combustion. As linseed oil cures, the process creates heat; quite a bit of it. If the rag is wadded up, there will be several surfaces concentrating the heat and the temperature may climb to the ignition point for the material.

Good point, thanks for clarifying.

While not needed the environmental conditions can accelerate the process.

 

[1018Machine]

Had it happen in the paint dept where I used to work. Solvent filled rags dumped in the rag bin! They should have known it was a no-no!

 

[Susquatch]

Good point, thanks for clarifying.

While not needed the environmental conditions can accelerate the process.

Yes, they can. But they are not as significant as the trapped heat. Basically, the ambient temperature has a linear effect while insulation has an exponential effect. The ambient temperature reduces or increases the temperature differential that drives the rate of heat transfer. But the curing process adds heat directly.

 

[Chicken lights]

We fed our hay to the cows. He sold his to the horse people, (they're crazy) and even 40 years ago they would pay 2-3$ per bale for a 40lb square.

Why is Canadian hay better? The only answer I've found that makes sense is ours is more nutrient rich. It's never made sense to me why hay or straw goes province to province or to the USA

It's also confusing straw gets called hay, like soybeans get called grain

 

[Doggggboy]

Straw is the stalks and stems of plants that are harvested primarily for the grain. Wheat, oats, barley, rye and others. It is used mostly for bedding for feed animals.
Around here in drought years if the grain crop is too poor to be worth harvesting for the grain, it is quite often cut and baled and used for feed.
Hay is usually the whole plant. Alfalfa, clover, Timothy grass, Brome grass, Russian wild rye grass. Used for feed.
Not sure if Canadian hay is better or not.
Having it go province to province or to the US quite often is dependent on local drought conditions. If you can't grow it, you gotta buy it.

 

[Susquatch]

Why is Canadian hay better? The only answer I've found that makes sense is ours is more nutrient rich. It's never made sense to me why hay or straw goes province to province or to the USA

I don't really know. But I almost went broke over it. While the ratio of daylight to nighttime hours changes as you go north or south and as the year proceeds, I doubt that it has a very major effect on the quality of the hay.

My guess is that it's really more of a supply and demand thing. Knowing what I know now, I'd never grow hay where I could grow corn. The profit per acre is WAAAAY higher for corn. But some ground won't grow corn so you grow hay there!

Weather plays a role too.

Bottom line is that I think the business case drives what farmers do when growing, selling, or buying.

The weather, soil, latitude, local supply and demand, and competitive pricing drive the business case.

 

[Susquatch]

Why is Canadian hay better? The only answer I've found that makes sense is ours is more nutrient rich. It's never made sense to me why hay or straw goes province to province or to the USA

I don't really know. But I almost went broke over it. While the ratio of daylight to nighttime hours changes as you go north or south and as the year proceeds, I doubt that it has a very major effect on the quality of the hay.

My guess is that it's really more of a supply and demand thing. Knowing what I know now, I'd never grow hay where I could grow corn. The profit per acre is WAAAAY higher for corn. But some ground won't grow corn so you grow hay there!

Weather plays a role too.

Bottom line is that I think the business case drives what farmers do when selling or buying.

The weather, soil, latitude, local supply and demand, and competition drive the business case.