Spontaneous combustion and your safe

[PinnedAndRecessed]

I read a couple of posts about gun owners soaking socks in oil, then putting handguns in the socks, then putting them into their gun safes.

Just curious, but is it possible that such an arrangement could lead to spontaneous combustion? I don't "soak socks in oil" but I do oil my guns before storing them, in my safe, in silicone treated socks.

(Yes, I took college level physics, but only made a 'C' so cut me some slack.)

 

[Marnoot]

Depends what kind of oil they were soaking them in. Boiled linseed oil, and (I think) tung oil both heat up as they dry/cure. I know you're not supposed to put rags soaked with either in the trash or an enclosed space until completely dry as they can spontaneously combust.

 

[PinnedAndRecessed]

or an enclosed space

From here:

http://www.newmarketfire.com/spontaneous_combustion.htm

if the oily rag was placed in a tightly sealed jar, it most likely would not have sufficient air to allow the oxidation process to occur

Is that what you were referring to?

 

[Marnoot]

Either "extreme" is safe for the rags. In a container small enough that there is little or no additional room for air, or in a very well ventilated area. Anything in between is asking for trouble. So it really depends how enclosed the space is. I would consider a safe to be in the dangerous range for enclosure. I've always layed them open flat outside.

 

[PGroenewold]

Rags soaked in BLO and placed in the trash will definitely spontaneously combust... don't ask me how I know this!

Older and wiser now,

PG

 

[distra]

Pinned, this is chemistry not physics Just kidding I doubt you have anything to worry about. Unless of course, your safe has a very oxygen rich environment and you increase the pressure a few atmospheres. With oil think of a diesel engine. You need to compress the atomized oil and compress the air/oil mixture to get ignition.

 

[Marnoot]

With oil think of a diesel engine. You need to compress the atomized oil and compress the air/oil mixture to get ignition.

With some kinds of oils (linseed oil as an example), heat is produced as they dry/cure/polymerize. Insufficient ventilation can cause this to lead to combustion of material soaked in said oil. No pressure or more oxygen than normal needed. See PGroenewold's personal experience.

 

[mete]

If it does combust the danger may not extend beyond the safe . The proper disposal for oil or solvent soaked rags is in aa container , designed for that purpose which is steel with a tight cover .

 

[Serendipity]

The diesel analogy is in no way accurate, relative to the subject being discussed. Spontaneous combustion of oily rags has nothing to do with atomospheric pressure and compression of atomized fuel.

 

[G T]

"Spontaneous combustion" is the slow oxidation of a fuel that slowly heats the surrounding fuel. This heating raises the rate of chemical reaction and the oxidation occurs more quickly and the temperature continues to rise until flaming ignition occurs or the ventilation limit is reached. That being said, I doubt that your sock is thick enough to ignite. This is because the temperature gradient from center to edge of the sock would be small due to the efficient convective cooling of the large surface area (relative to volume).

Sontaneous ignition is encouraged by small, insulated, lightly-ventilated enclosures like cardboard boxes. The small ventilation is enough to sustain the oxidation reaction while the size and insulation keeps the heat near the fuel.

Also, it's possible for big piles of wood to spontaneously combust. So it's not just oily rags.

Finally, the diesel analogy is not an accurate representation of slow spontaneous combustion. The combustion reaction in your car is a premixed reaction where the fuel and air have been mixed beforehand. This reaction is hot and fast. The ignition is called "spontaneous" only because people don't see a spark; in truth, the high temperature and pressure drive the air/fuel mixture way past the ignition point and thus it ignites. The sock example of spontaneous ignition is a diffusion process where the fuel has to be extracted from it source (e.g. sock) and is a much cooler, slower process. It can take days or weeks for a reaction to foment into a flaming fire.

 

[PinnedAndRecessed]

The sock example of spontaneous ignition is a diffusion process where the fuel has to be extracted from it source (e.g. sock) and is a much cooler, slower process.

Regardless of external temperature? Can this phenomenon occur in freezing temperatures? Room temp?

I.e., does the temp have to be hot for this to occur?

 

[CB900F]

Pinned;

I'm a locksmith who's been dealing with safes for years. I've never even heard third-hand rumor from the hairdresser's cousin's girlfriend's significant other 'who's a real big dude in the safe business', about this happening.

I think the chances are so vanishingly small, that you'd have to have a deep psychological need to drive yourself nuts over it, said need occuring for other reasons.

900F

 

[G T]

Regardless of external temperature? Can this phenomenon occur in freezing temperatures? Room temp?

I.e., does the temp have to be hot for this to occur?

Spontaneous ignition most often occurs with the fuel initially at room temperature. Hotter environments will promote spontaneous ignition: it's like giving the reaction a head start.

It's unlikely that freezing temperatures will allow spontaneous combustion for most fuels because the time for heating to occur may be on the order of years instead of days.

EDIT: Forgot to mention that a cooler environment promotes more efficient cooling. Therefore, in a sufficiently cold place (which may be freezing for your fuel) enough of the heat can be conducted away to prevent temperature rise. This will prevent ignition.

 

[230RN]

More and less likely likely situations for for spontaneous combustion

In addition to the above remarks on the likelihood of spontaneous combustion occurring:

Many other things besides oily rags will spontaneously combust if the parameter of "just enough but not too much" ventilation occurs.

Examples:

Bales of hay, if not properly stacked with at least a hand's breadth between the bales, may catch fire, although the initial heating is usually due to fermentation rather than slow oxidation. Many barn fires have started because of this phenomenon.

Large piles of iron or steel shavings will start burning if they've been slightly wetted. The initial rusting is exothermic (gives off heat), which leads to more rapid rusting, which gives still more heat. Since steel shavings are often oily as well, the phenomenon is worsened by the presence of the additional fuel.

Altitude has an effect on the likelihood of spontaneous combustion. The lower the partial pressure of oxygen (as at higher altitudes), the less likely that spontaneous combustion will occur --it is more likely to happen at the Dead Sea (200 ft below sea level) than the top of Pikes Peak (14,000 ft above sea level).

Partial Pressure example: Bearing in mind that sea level air pressure is 14.7 psi absolute (760 mm Hg), and the air contains 21% oxygen, the partial pressure of oxygen at sea level is about 3.1 psi absolute (160 mm Hg) and at 5280 ft altitude is close to 2.6 psi absolute (133 mm Hg).

 

[mete]

A study of the sinking of the battleship 'Maine',[which started the Spanish American War], by Admiral Rickover ,concluded that itwas a problem of spontaneous combustion of the coal not Spanish mines or torpedoes.. There was a design problem of the Maine and some other warships in that the coal bunker was adjacent to the powder magazine !! Spontaneous combustion of coal was one of the hazards in those days.

 

[meef]

And then there's the supposed phenomenon known as "spontaneous human combustion" which allegedly will result in you making an ash of yourself without even having to imbibe so much as one freakin' beer.





.... we now return you to your regularly scheduled thread ......

 

[distra]

Au Contraire, check the MSDS sheets for linseed oil and S&W gun oil
http://physchem.ox.ac.uk/MSDS/LI/linseed_oil.html
http://www.gunk.com/msds/SW001.PDF

Two very different beasts. Unless you are refinishing your grips, I doubt you have much to worry about. Both material should be kept away from strong oxidizers, for example high O2 concentrations.