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Thread: DC chip vs fine dust collection

  1. #16
    Alan, that is a very interesting data point. I don't have any way to measure air quality. But I do have an overhead air cleaner. After turning off the dust source about how long does it typically take to get the particle count down?

    I am wondering because I don't like running the overhead air filter . It is a little loud and most of my time in the shop is spent quietly with hand tools. I would prefer to turn it off after it has done it's job.

    Lets see a little back of the envelope calculation: my garage is 22x22x11 = ~5k ft^3. My Jet says it moves ~1k ft^3/minute. So it will process the volume of air of my garage in ~5 minutes. But how much of that is just the same filtered air being recirculated? Would nee a lot more math to improve the accuracy and lots depends on how efficiently the air moves around the shop. And also the efficiency of the filter. Looks like mine is only 85% at 1 micron. So I am probably looking at 3-4x the time to get the count down.

    Thanks!!
    Salem

  2. #17
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    So it seems that using the Dylos particle counter explodes one myth that seems to get repeated over and over, the one that says that the ambient air cleaners are nothing but "dust blowers". And wasn't that term coined by one of the gurus of dust collection?

    Personally I am happy that I have one of those dust blowers, as I can't tell you how much dust my DC DIDN'T catch yesterday when I made at least a dozen 5 cut method tests trying to zero out my table saw sled. Using a sled to take a sliver off a cut is one of those operations that table top collection sucks at, particularly when you can't use your Shark Guard.

  3. #18
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    Pardon my disagreeing Ole, but i don't think anybody has (that i've seen anyway) ever said that a functional ambient cleaner doesn't help clear the air. The objection that gets raised time and again is that they by definition can't function until the air we're breathing is full of dust, that we end up breathing this dust until the air has cleared, and that consequently it's inadvisable to design a system to require the use of one.

    Bill Pentz and lots of others routinely instead steer people towards their targeting a system and hooding arrangements that capture the dust at source.

    The other issue that Bill has raised that militates against using an ambient cleaner is that leakage means that you end up with a shop layered with dust. Dust that gets stirred up every time you move, and which can easily result (if the reported numbers are true) in particle counts much like those caused by machines with poor dust collection.

    It's all very well taking a Dylos reading after the count has dropped and consoling yourself that it's fine. The issue is that (a) the medical limits are very low (they typically specify dust limits in terms of steady levels (1 - 5mg/m3 or better) maintained over an 8hr day), and (b) you take a significant hit while waiting for this to happen. The standards are presumably pitched as low as they are they are for some reason.

    The 'dust blower' comment or whatever that i saw related to recirculating systems fitted with filters that allow the fine dust to blow straight through - because the media fitted is too coarse to catch fines. This targeted the older style bag filters that used a fabric with large openings. It's applicable too to good quality filters that have started to pass dust as a result of wearing out or being damaged.

    The tougher question is whether or not a properly functioning high CFM system can capture the dust in all possible cutting situations. The answer to that one is presumably that 'it depends'. Depends if nothing else on having hooding arrangements that work for the task in hand....

    ian
    Last edited by ian maybury; 01-28-2012 at 10:27 AM.

  4. #19
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    Guess you can count me in as one of those whose DC systems are woefully inadequate as I also have an overhead dust blower arounder. At least that's what I'm surmising from all of these repeatitive posts........in 500 words or more......in every dust collection thread on this forum.

    Me, I'll stick to contributors like Phil Thein, who use logic and common sense in their approach, instead of nebulous, ambiguous references and run on sentences that come to no conclusions.

    I'd much rather spend my time in the shop actually woodworking than spending every spare dollar and moment trying to calculate and acquire the ultimate DC system.

    What was that term again? Oh yea, post purchase rationalization.

  5. #20
    Quote Originally Posted by Ole Anderson View Post
    So it seems that using the Dylos particle counter explodes one myth that seems to get repeated over and over, the one that says that the ambient air cleaners are nothing but "dust blowers". And wasn't that term coined by one of the gurus of dust collection?
    I think BP was referring to the 30-micron bag DC's as dust blowers.

    Although he did say air cleaners take hours to work. Here (source: http://billpentz.com/woodworking/cyc...conversion.cfm):


    Many wrongly think all you really need to protect yourself from fine wood dust is a good mask. A good mask only protects you while working. Few leave their masks on long enough. Using an air cleaner or even a modest sized exhaust fan takes about six hours to clean your shop air amply to take off that mask.
    IMHO, the Dylos meters exploded a bunch of myths. The particle counters have done a great job exposing a lot of what was once thought to be gospel as little more than marketing hype.

  6. #21
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    The ambient air cleaner issue seems unfortunately to not be that simple guys. Fine Woodworking for example ran a 'happy' piece on them, and were persuaded into a retraction by one of the makers of cyclone based dust systems. The letter of complaint, and a link to the revised piece are here on the FWW website: http://www.finewoodworking.com/item/...leaner-article

    If i've correctly understood the gist the piece it pointed up at least two basic problems:

    (a) Casual particle count readings, or readings that don't address the full range of particle sizes produced in woodworking may seriously underestimate the reality of exposure for the woodworker.
    (b) Ambient air filters anyway are not regarded as being capable of meeting the ACGIH, EC and NIOSH air quality standard. (the oft quoted 1mg/m3 TLV)

    Pardon my banging away on this. It's not about winners or losers, it's about practical facts and their likely implications for health.

    Pardon my less than specific responses too. It'd be great for everybody (myself included) if the engineering and other elements that make up a functional dust system could be expressed in words of one syllable. The problem is that it's not that simple - it depends on the specifics of the situation.

    The clear implication of the regulations and the associated CFM recommendations though is that it's normally possible to make the required TLV with a higher CFM/HEPA filtered/collect the dust at the source system of the sort being discussed, but much less so with lower CFM.

    That doesn't mean that committed guys like Phil can't finesse a lower CFM system into doing the business in certain situations, and it equally doesn't mean that installing a DIY high CFM system guarantees success. There's quite a few factors that have got to be got right in either case.

    The result is that when posting i point to bits of information addressing the points that arise - but after that it's for each and every one of us to do our homework and decide accordingly.

    As a punter much like everybody else i know only what i've informally read on the topic and learned in the course of building my own Pentz system. I've seen the difference in performance it's delivered compared to the 1kW bag filter i struggled with for years before, but i've not measured the result - so for all these reasons and more i'm most certainly not prepared to make hard and fast recommendations that may not stand up....

    ian

  7. #22
    Quote Originally Posted by ian maybury View Post
    The ambient air cleaner issue seems unfortunately to not be that simple guys. Fine Woodworking for example ran a 'happy' piece on them, and were persuaded into a retraction by one of the makers of cyclone based dust systems. The letter of complaint, and a link to the revised piece are here on the FWW website: http://www.finewoodworking.com/item/...leaner-article

    If i've correctly understood the gist the piece it pointed up at least two basic problems:

    (a) Casual particle count readings, or readings that don't address the full range of particle sizes produced in woodworking may seriously underestimate the reality of exposure for the woodworker.
    (b) Ambient air filters anyway are not regarded as being capable of meeting the ACGIH, EC and NIOSH air quality standard. (the oft quoted 1mg/m3 TLV)
    The letter from Mr. Witter complains that the author only measured .1 to 10-microns, ignoring everything above that size. And from a scientific perspective, I suppose it would have made more sense to be more exhaustive. From a common-sense perspective, however, if the air cleaner is removing everything from .1 to 10-microns (quickly), I'd imagine it is getting anything 10-micron and larger.

    I think the original article (which I had read) did leave the impression (at least somewhat) that the reader only needs a good air cleaner. I think this may have been an unfortunate result of trying to communicate just how well air cleaners work, not an effort by the author to actually communicate this was his opinion.

    Used alone, an air cleaner certainly will not meet any air quality standards. Neither will a 1-1/2 horse DC or a huge cyclone. Air cleaners are like the old BASF (chemical company) commercial. The BASF commercial said "we don't make the paint, we make the paint better." Well, air cleaners don't make the dust collection system, they make the dust collection system better.

    Nonetheless, both the original article and the follow-up do a good job, IMHO, of explaining just how well an air cleaners can work.

    Quote Originally Posted by ian maybury View Post
    Pardon my banging away on this. It's not about winners or losers, it's about practical facts and their likely implications for health.

    Pardon my less than specific responses too. It'd be great for everybody (myself included) if the engineering and other elements that make up a functional dust system could be expressed in words of one syllable. The problem is that it's not that simple - it depends on the specifics of the situation.

    The clear implication of the regulations and the associated CFM recommendations though is that it's normally possible to make the required TLV with a higher CFM/HEPA filtered/collect the dust at the source system of the sort being discussed, but much less so with lower CFM.

    That doesn't mean that committed guys like Phil can't finesse a lower CFM system into doing the business in certain situations, and it equally doesn't mean that installing a DIY high CFM system guarantees success. There's quite a few factors that have got to be got right in either case.
    I think the important point from all of this is that a large cyclone with big ducting is no guarantee of success.

    Similarly, a 1-1/2 HP DC, with 4" ducting is no guarantee of failure.

    Sorry to keep hammering on that. But for some time, some have been preaching just the opposite. The emperor's tailors had a lot of people convinced we needed $2500 worth of gear to get safe DC. The particle counters have lifted a veil, if you will. I really feel the particle counters have exposed some conventional wisdom for what it really is: conventional marketing.

    Quote Originally Posted by ian maybury View Post
    The result is that when posting i point to bits of information addressing the points that arise - but after that it's for each and every one of us to do our homework and decide accordingly.

    As a punter much like everybody else i know only what i've informally read on the topic and learned in the course of building my own Pentz system. I've seen the difference in performance it's delivered compared to the 1kW bag filter i struggled with for years before, but i've not measured the result - so for all these reasons and more i'm most certainly not prepared to make hard and fast recommendations that may not stand up....

    ian

  8. #23
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    I think the bind that FWW found themselves in might have been that by measuring only 1-10 micron particles the mg/m3 readings they produced ended up artificially low. i.e. The larger proportion by weight of the dust produced by typical power tool processes is made up of larger sized particles, and is included in the regulated 1mg/m3 limit. With the result that their results were very different to (and much lower than) what regulatory testing would have produced in the same circumstances.

    The clincher was that the ambient air cleaners all allowed the dust levels in the room to get way above the regulated limit for quite some period. They were overwhelmed by the rate of dust production (which suggests that if a machine is in continuous or more frequent use a cleaner isn't going to be of much help), and didn't catch up until some time after the dust production ceased. Trouble was they didn't call this.

    They could i suppose have dug in and said 'it doesn't matter', there's no regulation of air quality in the hobby/DIY environment, and we think these units are doing a great job. But saying that in the face of the regulated limit would have begged rather more fundamental questions about the test.

    Anyway. I think Phil we can agree that 'you can never say never', but i won't be rushing to change my system for a lower CFM model...


    ian

  9. #24
    Quote Originally Posted by Phil Thien View Post
    I think the important point ... is that a large cyclone with big ducting is no guarantee of success.

    Similarly, a 1-1/2 HP DC, with 4" ducting is no guarantee of failure.

    Sorry to keep hammering on that. But for some time, some have been preaching just the opposite. The emperor's tailors had a lot of people convinced we needed $2500 worth of gear to get safe DC. The particle counters have lifted a veil, if you will. I really feel the particle counters have exposed some conventional wisdom for what it really is: conventional marketing.
    +100

    And isn't it more important that the air quality of the hobbyist's workshop is somewhat better than somewhat worse? For years, I've been working in a shop that got cleaned, sporadically, with broom and dustpan. Then I got a shop vac. I built a top hat separator based on Phil Thien's research. The damn thing works great. But my shop is still coated in dust. Why? Because I only use the shop vac when things get so bad I can't stand it anymore--or when I can't find a tool because it's camouflaged under the same film of dust as everything else.

    So I'm gonna build a central dust collection system. I don't have $3000 to invest in a cyclone and 8" spiral duct. But I can install 4" PVC and hook it up to the Central Machinery dust collector I got on coupon sale from Harbor Freight. I can also put together an air cleaner with this old furnace fan I have and some filters.

    Will my system meet government standards for clean workshop atmosphere? No, decidedly not. But will it make my workshop environment a little bit healthier? Yeah, I think so. And, if I don't die beforehand (from old age, not from excessive dust inhalation), I get to the point where I am actually realizing a profit from my hobby and can install a better system, I will.

    But I am sick and tired of all the horror stories that if I don't have this cyclone or that spiral metal duct, I will kill myself from breathing too much dust. The chances are significantly higher I will kill myself trying to heave a sheet of 3/4" plywood onto the table saw.

    Thanks to Phil and Ian for this discussion. I'm not taking sides, but I'm not gonna be terrified about a less-than-perfect dust collection system, either.

  10. #25
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    Quote Originally Posted by Thom Porterfield View Post
    +So I'm gonna build a central dust collection system. I don't have $3000 to invest in a cyclone and 8" spiral duct. But I can install 4" PVC and hook it up to the Central Machinery dust collector I got on coupon sale from Harbor Freight. I can also put together an air cleaner with this old furnace fan I have and some filters.

    But I am sick and tired of all the horror stories that if I don't have this cyclone or that spiral metal duct, I will kill myself from breathing too much dust. The chances are significantly higher I will kill myself trying to heave a sheet of 3/4" plywood onto the table saw.
    Regarding the "marketing hype" of this topic, there some engineering aspects that many woodworkers ignore. Specifically, in engineering one can't generally design a single system that does all things well, and by using 2 or more systems that are each designed for a specific section of the problem, one can generally save a good deal of capital investment and operating costs.

    Specifically, many quite expensive dust systems contain a squirrel-cage blower type of DC with a HEPA (High Efficiency Particulate Air (some substitute "arrester" for the "air" part in the abbreviation) filter on top, sometimes with a motor-powered inside scraper and either an internal or external cyclone.

    The problem with these designs is that bey their very nature, a HEPA filter has a large pressure drop across the filter (i.e., it takes a lot of air pressure to force air through the filter). Because the motor sizes on many DC systems aimed at home WW shops are limited by both cost and the usual 16 amp limit for running the system on 120V, 20Amp household circuits, the introduction of a HEPA as a final filter significantly affects the system performance - and not in a good way. A filter bag type system that most of us are familiar with from a few years ago typically has a considerably higher CFM than a DC with a HEPA filter, but they won't catch really fine dust, which is the most harmful.

    So - there is a very amenable solution that is considerably cheaper and far more efficient - use a filter-bag type DC for machines that produce large chips and very little fine dust and require a very high cfm to remove the chips efficiently and prevents clogging of the machines and the DC ductwork - that would typically be jointers, planers, and powered saws. For sanding, where one isn't concerned nearly as much with high CFM as high efficiency particle filtration, use a common shop vaccum with an internal bag and HEPA final-stage filtration. Used with an efficient dust collection attachment fitting at the source of the generation ( ROSs or belt sanders), a very inexpensive shop vacuum is highly efficient at capturing and filtering the air.

    Such a solution makes a DC that you can run on 120V household current far, far more efficient, and the shop vac solution is far better for fine dust; just one such reason is that you can run an internal bag in the shop vac before the HEPA stage, so disposing of the fine dust is far cleaner than opening up a large DC that is filled with both chips and fine dust.

  11. #26
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    Quote Originally Posted by Phil Thien View Post
    I think BP was referring to the 30-micron bag DC's as dust blowers.

    Although he did say air cleaners take hours to work. Here (source: http://billpentz.com/woodworking/cyc...conversion.cfm):

    Many wrongly think all you really need to protect yourself from fine wood dust is a good mask. A good mask only protects you while working. Few leave their masks on long enough. Using an air cleaner or even a modest sized exhaust fan takes about six hours to clean your shop air amply to take off that mask.
    IMHO, the Dylos meters exploded a bunch of myths. The particle counters have done a great job exposing a lot of what was once thought to be gospel as little more than marketing hype.
    Ole may not be talking about BP, you see the dust blower comment applied to air cleaners made here on a regular basis.
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  12. #27
    Quote Originally Posted by Van Huskey View Post
    Ole may not be talking about BP, you see the dust blower comment applied to air cleaners made here on a regular basis.
    If I'm mistaken, I apologize.

  13. #28
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    Quote Originally Posted by Joe Leigh View Post

    Me, I'll stick to contributors like Phil Thein, who use logic and common sense in their approach, instead of nebulous, ambiguous references and run on sentences that come to no conclusions.
    What you are doing is what everyone in this life does, cherry pick the information to suit yourself. Stick to your guns and don't let anyone tell you any different, they are your lungs so you should be responsible for them.
    Chris

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  14. #29
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    Quote Originally Posted by Van Huskey View Post
    Ole may not be talking about BP, you see the dust blower comment applied to air cleaners made here on a regular basis.
    Thank you. Yes, I have seen the "dust blower" analogy applied both to ambient air cleaners and to older bag style dust collectors. Maybe we ought to start referring to what we are speaking of as a "dust management system" that would include respirators, dust collection systems, machine "hoods", ambient air cleaners, shop vacs and the trusty broom and dust pan. Any one of those alone will never provide us with an acceptable dust level as far as our lungs are concerned, you really need every one of those in order to address the problem.

  15. #30
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    As I read this thread it seems that taking sides in this discussion misses the point of the information. There are a million variables that affect DC efficiency. Each person needs to evaluate his own needs rather than rely too heavily on any of our opinions. What size machines are run, what type of cutterhead, as each affect chip type and cfm needs. Drum, belt, and edge sanders add huge complexity in determining the type of cyclone design, filter media, and fan type needed. The size of the shop is a huge variable. My 2000 sq ft shop has two overheads but most likely needs four as they take too much time to bring the Dylos count down. I have changed out piping more than once due to testing each port with an anemometer and finding my best guesses weren't exactly optimal. Each of us, if we are concerned about air quality, must do our own testing and not just rely on what others tell us. There is too much conflicting information and too little real testing for conclusions to apply to our own specifics. My Dad died on oxygen and my lung capacity isn't what it used to be- but most of my other parts aren't either- so I started testing my own stuff. I encourage others to do the same. These discussions should not replace individual responsibility for determining what is the correct application for our type of woodworking. Dave

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