*Putting* water in your DC collection bin?

[George]

Yeah, me too. So how is it you have such contempt for precise knowledge?

Not theory, but fact. Once again, that's what science is - reproducible, and everywhere the same.

[Dave Hinz]

Yeah, me too, WHAT? WTF are you responding to, George? You don't even see with this blatant example, why your insistance on top-posting inhibits communication? I have no contempt for precise knowledge. Why don't you try exhibiting some and we'll see if you can.

I notice you ignored this. Do you have _any_ point to make here, George, or are you just making noise to listen to yourself?

[George]

Venn diagrams are meaningless in cause-effect relationships. "Communication" with the unreasoning is impossible.

I would expect some> > Yeah, me too. So how is it you have such contempt for precise knowledge? >

[G. Lewin]

That's quite a brash statement (that they outgas the same). But I like the way you make brash (or ambiguous) statements and then mock everyone who disagrees. It makes the internet worth while.

Anyway, to the matter at hand...a cursory search of the internet, which as we know never provides false information, shows many examples of spontaneously combusting sawdust, albeit usually at the bottom of a 20' mound. I did, however, find an example of a fire caused by a "pile of sawdust under a sawbench." How big a pile? I dunno'. See:

Likely, the dust was from green wood.

-----

Now, because of the nature of the danger, this problem has actually been studied (believe it or not, we need not concern ourselves with hay fires!). The following absolute truth was also found on the internet:

From :

"As with compost and rubber tyres, wood chips and sawdust material can undergo self-heating reactions, leading to spontaneous combustion, under certain storage conditions. Factors that will play a part in whether self-heating leading to combustion will occur are the size of the wood chips, the moisture content, the presence of other flammable waste materials within the stockpile that are easily ignitable, and the natural oil content of the wood. Sawdust has been tested extensively[1] over any years and it has been found that the greater the proportion of oil present in the wood, the lower the critical ignition temperature (the temperature at which a runaway reaction occurs)."

1. Bowes, P C. Self-heating: evaluating and controlling the hazards. Building Research Establishment. Department of the Environment. 1984. HMSO.

It seems this Bowes fella' made a career out of this stuff. Even though he died in 2001, he was nice enough to write it all down in a book. Sadly, now that I'm no longer a student, I can't get my hands on it easily. But maybe if one of you could find it, it could settle the matter of whether or not s.c. is possible in this case. It might also answer the more immediate question of who can piss farther.

In the above, I note the following:

1) Oil content is critical. How much oil is in sawdust from green wood vs. dust from air dried vs. kilned, I don't know. Anyone?

2) Note that several other factors, including other oil sources are important. This certainly has bearing on the original poster's question. Does, for example, it make a difference if he cuts plywood or any other source of organics? What if he hacks up an old project that was treated with linseed oil?

I suspect that if one read the book, you'd be hard pressed to make a case for s.c. at this small a scale (especially since the water content must be just right); nevertheless, I bet you _could_ come up with a scenario, albeit unlikely. Would I worry about it? No. But I'm not silly enough to put water in my DC system...

-----

As for hay, I found this incontrovertible evidence (of course, because it's on the internet):

From

"Hay fires usually occur within six weeks of baling, but they may occur in hay several years old. Fire can occur in loose hay, small bales, large bales or in stacks. The fires can occur in hay stored inside as well as in hay stored outside. Regardless of when or where the fires occur, the most common cause is excessive moisture."

Note that "old" hay is also subject to s.c., the point being that once dried, s.c. is rare because, well, it's dry. But if re-wetted, I see no reason why bacterial growth can't restart. Of course the C:N ratio of wood is so high that it's hard to get a lot of bacterial growth and heat production, but that obviously happened in the s.c. examples above. I have certainly felt warmth in sawdust piles, but they were outside where heat/organics couldn't build up enough for s.c.

Anyway, the point is that if you want to claim that hay and sawdust outgas the same, then if old hay can s.c., then surely you agree that old sawdust can, too. Yes?

Well, of course there is. But if we don't understand _all_ of the factors involved, then changing the input (cause) may lead to an unexpected result (effect). That is why scientists have jobs -- because not everything is understood.

Enjoy,

Greg

[Dave Hinz]

Good lord. You must be being _intentionally_ dense.

Of the set of all objects which are causes for spontaneous combustion, some of them apply to manure. Some of them apply to hay. Some of them apply to oily rags, and so on. Oily rags are not cow manure. Sawdust is not oily rags. Wet hay is neither.

I've noticed that.

I have plenty of respect for science, communication, and learning. You continue not to exhibit any of those.

Third time: (I bet you'll evade it again) Are you saying that spontaneous combustion of sawdust is impossible?

[J. Clarke]

There's also how much oil in one species vs another, say Southern Longleaf Yellow Pine heartwood vs some comparatively oilless species, and the composition of the oil--Lapacho for example is about as combustible as concrete, despite being oily enough that you can polish it with its own secretions.

[RichardC]

It's amazing, ?..like whispering a word around a circle, when we were kids, and finding it returned indistinguishable from its beginning. This may be a bit hasty, but, I am concluding from my experience reading both the Cruising World Sailing Board and Woodworking Rec, any thread greater than 7 entrees is bound to be off topic by the 8th. I can imagine, though, with some concentrated imagination, how some were able morph DC into Dogs and Cats. Regards, Richard