# dust collection ducting

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• posted on January 27, 2005, 1:14 pm

Insert "of an empirical event" after the word "probability" in the last sentence and I agree. Logically false (as opposed to empirically false) statements do have a zero probability of being true.
"A and B and (A implies not B)" has a zero probability of being true.
But as someone said, we are picking fly specs out of pepper here. I think LRod cited an interesting article pointing out the baselessness of concerns about dust explosions from ducting. While he might have slightly overstated the article's conclusions, those who are reacting negatively to his absolutism (and I tend to be one who so reacts) are missing or avoiding the message of the cited article.
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Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

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• posted on January 27, 2005, 1:49 pm

You have a single die (a regular hexahedron, with the faces labeled "1", "2", "3", "4", "5", and "6".
What is the probability of rolling a "7" ?
I do believe that saying "exactly identical to zero" _would_ be an accuracte answer.
I'll willingly agree that the _question_ could be considered 'inherently incoherrent'. <*grin*>
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• posted on January 27, 2005, 3:33 pm
Probabilities are measured on a scale of 0 to 1.
Even a "zero" probability is not an indication that an event will never happen.
A zero probability states that an even "almost never" happens. A probability of one states that an event "almost always" happens.
Therefore, probability theory would state that, while the probability of rolling a 7 is zero, there is still a chance (however small) of it occuring.
Let me put this another way. Prior to 9/11/2001, most Americans would have said that the probability of two airliners striking both towers of the World Trade Center within minutes of each other and destroying both, was zero.
Yet, it DID happen.
LRod actually did make a cogent point in one post that he was willing to settle for a "reasonable estimate". That is actually a good way of explaining the situation.
The lesson to be learned here is to refrain from making absolute statements like "zero chance".
Gus
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• posted on January 27, 2005, 5:09 pm

The problem with this analysis is that it attempts to compare two entirely different hypotheses. While the events of 9/11 were certainly unthinkable and had, even if considered, an extremely low probability, the fact is all of the mechanisms to make it a an eventual reality were always in place.
In the case of the six sided die, there isn't any chance, not one, zero of a seven coming up. It isn't physically possible. There are only six choices--six possibilities. A seventh possibilty does not exist. There is zero chance for it to occur.
But obviously six (or seven) events is too complex for some of our members. Let's make it simple. The classic example for demonstrating probability is tossing a coin. Whenever the event is postulated it is always expressed as, "what is the possible outcome of a coin toss," or words to that effect. The answer of course is either "heads" or "tails."
One can then calculate and demonstrate all of the probability machinations one wants on the probability of any particular toss, however, if one were to say the probability of a toss coming up turkey feathers (or cream of tartar) is zero but could still occur is utter nonsense since turkey feathers is not in the set of possible outcomes. There is zero chance of getting turkey feathers from a coin toss.
In order for there to be probabability there must be possibility. The burning helium mentioned earlier is an example. Can't happen. The laws of physics (or more accurately, chemistry) dictate this. One can't even express a probability of it happening.Those who don't know where to find these "laws of physics" need read no further; the rest will be far too complex.
I made my point about an estimate because I knew it must include the word "zero" which is what seems to have so many up in arms.
Now, having said all of that, I will concede this: "zero chance" or absolutism, as one of my fans described, may not be technically accurate when measured to the painfully smallest degree. However, if you are living life in a real world, breathing real air, eating real food, driving real cars on real streets, hey, if you're woodworking with real wood and real tools, then you are already engaging in countless activities all of which have probabilities of danger orders of magnitude higher than an explosion of dust in a home shop dust collection system. That anyone would pick the demonstrably miniscule potential of that event on which to take a stand on personal risk management makes me double over in mirth.
- - LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
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• posted on January 27, 2005, 5:11 pm
Gus wrote:

This isn't a math ng, but this is simply wrong...the probability of generating a value outside the set of possible integral results of any discrete function is identically zero.

After which the probability was identically one...the problem here is that a hunch or opinion is not a mathematical probability and much experiment has been done to show that people hold opinions of likelihoods of events that are far from being mathematically consistent...but, given the question you posed I don't really think most would have actually said "zero" but given something on the order of "highly unlikely".

Except, of course, when there really is zero chance, which in the case of the potential for dust explosions is <not> identically zero. This assertion detracts significantly from the point attempted to being made as a cogent argument--it just isn't.
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• posted on January 27, 2005, 6:19 pm

That's a pretty novel understanding of probability theory! How large does the chance of something happening have to be before its probability gets to be non-zero? <G>

Which is dramatically different from what you said before. You seem to be confusing the probability of an event with what most Americans would say the probability of that event was.

yep. And maybe that "reasonable estimate" is 1/1000th of the probability of all life on Earth being destroyed in an asteroid hit. Risks like that I can live with!

I agree.
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Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

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• posted on January 28, 2005, 3:42 am

True, see my other post

This is imprecise and incorrect

No, in a set consisting of the elements not only does the probability of selecting a 7 from that set = 0, it is an impossible event since 7 is not *in* the set.

This is confusing fact and opinion. The answer to the question, do you think this will happen and getting the answer, "no" is an opinion. The facts were a) the twin towers exist in physical space on Earth, b) airliners are capable of flying within the atmospheric envelope and spatial area occupied by the twin towers, c) there is no physical barrier to airliners and the twin towers spatially intersecting one another. A more apt analogy for the impossible event would be, "can airliners strike two lunar landing sites within minutes of each other and destroy those historic sites?" There, the answer is the impossible event because a) airliners are incapable of operation the vacuum of space, and b) airliners do not have the sufficient thrust to leave the gravitational field of the earth.

+--------------------------------------------------------------------------------+ The absence of accidents does not mean the presence of safety
Army General Richard Cody +--------------------------------------------------------------------------------+
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• posted on January 28, 2005, 12:55 pm
Mark & Juanita wrote:

All of which strays far from the point of dust explosions.
They can and do happen.
The point, again, is to refrain from absolutism.
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• posted on January 28, 2005, 2:13 pm
My Brains full....can I go home...;)
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• posted on January 28, 2005, 7:10 pm
On Fri, 28 Jan 2005 07:55:53 -0500, Steve Decker

All of which begs the challenge I originally posed: cite a single example of a dust explosion occuring in a home shop dust collection system.
With your absolute certainty that they do, it should be dirt simple to find a cite. Just one. Come on. You know everything. Surely you can come up with one verifiable example. I'll leave the wreck forever if you can come up with a single documented instance.

Uh, where does that leave "[t]hey can and do happen"?
- - LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
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• posted on January 28, 2005, 10:12 pm
Whatever.
You win, LRod!
You da man !!
Now hear this everyone:
LRod hath decreed that there will NEVER, EVER, NEVER be a home shop dust explosion. Not EVER. ZERO chance. ZIP, ZILCH. NADA !
Let all Rod's people say AMEN.
You has done converted this wayward sinner, LRod.
Can I get a AMEN ? I has SEEN DA LIGHT !
Now everybody shake hands and go make sawdust !
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• posted on January 28, 2005, 10:41 pm

If I've only converted one, it was worthwhile...
Thank you.
- - LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
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• posted on January 29, 2005, 2:40 am
wrote:

ROTFLMAO!! Greg
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• posted on January 28, 2005, 10:52 pm

My, this sure has become a testy place of late. Maybe someone ought to fart and break the tension...
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-Mike-
snipped-for-privacy@alltel.net
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• posted on January 29, 2005, 4:40 am

AMEN!
djb (Who be sorely tired of this topic coming up again, and again, and again, and again, and again)
--
"The thing about saying the wrong words is that A, I don't notice it, and B,
sometimes orange water gibbon bucket and plastic." -- Mr. Burrows
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• posted on January 29, 2005, 1:55 am
wrote:

To be exact, no example of a dust explosion occuring in a home shop dust collection system as a result of a static spark ignition can be cited. It may be possible to cite examples of fires caused by metal debris contacting the impeller and causing a fire by spark or heat.
Problem is, static electricity does not have enough energy to ignite the size of particles present in a home dust collection system.

+--------------------------------------------------------------------------------+ The absence of accidents does not mean the presence of safety
Army General Richard Cody +--------------------------------------------------------------------------------+
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• posted on January 29, 2005, 6:32 am
On Fri, 28 Jan 2005 07:55:53 -0500, Steve Decker

but not in home shop dust collection systems from static discharge from plastic piping.
time to put up or shut up, steve.
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• posted on January 29, 2005, 11:30 am
Steve Decker

sigh...
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• posted on January 29, 2005, 12:38 pm
snipped-for-privacy@all.costs wrote:

As it happens, friend, I didn't say anything about home shop, plastic yadda yadda in that particular post.
Dust explosions, including wood dust, can and do happen and are well documented. We all have LRod to thank that one will never ever happen in a home shop.
Now as Gus says, I'm going to make some sawdust.
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• posted on January 31, 2005, 10:47 pm

Izzit OK if I bring that bucket of water back in the garage?