Thread: Fine dust Problem??

Hi Mates,

When we talk about woodworking dust collection we get ourselves into the middle of a vendor created confusion of identical terms meaning very different things. We have had standards to prevent fires and slipping in shops since the 1920s. The potential of explosive mixtures of wood dust and air have been a similar concern for nearly as long. That is why most standards organizations require not only putting our dust collection equipment outside, but also behind an explosion proof barrier.

This pretty much was the extent of concern about wood dust collection except for a few woods such as Western Red Cedar which is a pretty strong irritant so ended up with special controls to minimize exposure to it. Two additional things had to come together to push for much better fine dust collection. First, far too many full time factory woodworkers ended up getting ill and the medical researchers tied their illnesses to the various unhealthy aspects to the chemicals found in different woods. A good wood toxicity table such as the one on my web pages will help you to become more aware of these chemical risks. And second, researchers also discovered that all fine particles cause a measurable loss of respiratory capacity and some of each loss becomes permanent. This means like smog wood dust poses a double threat, the chemical in wood can be very unhealthy and the particle sizes can do us harm.

Our bodies do a pretty good job of getting rid of the particles sized about 10-microns and larger, but smaller particles tend to get past our normal protections. Particles sized below about 0.1-microns tend to mostly be exhaled. It is the particles in between that tend to cause problems. Those sized 5 to 10-microns tend to lodge in our major airways. Smaller particles down to about 1-micron lodge in our lung tissues and it appears particles sized under 1-micron can get right into our blood. Regardless, the issue becomes much worse when we realize that these trapped sharp particles not only do mechanical damage, they also can continue to release chemicals for quite a while. In fact, what launched me on my dust collection efforts was having a violent allergic reaction that went off about three weeks after I finished my last woodworking project. It turned out I had no idea that I had badly contaminated my home with so much fine dust that with my working from home my exposure was near constant. When that allergic reaction landed me in the hospital it did not stop even after they put me into a clean room because the dust trapped in my respiratory tissues just kept releasing chemicals.

What blindsided me was a clean looking shop that build up dangerously high amounts of fine invisible dust. The 10-micron and smaller particles are invisible without magnification. I installed the top magazine rated cyclone with vendor designed ducting and vendor recommended upgraded filter. That so called 1-micron filter actually filtered off all the 10-micron and larger particles and acted as a storage depot for the finer particles. Just turning on that system without doing any woodworking created such a high airborne dust level from residual dust that my air quality inspector made us both put on our masks. To make matters even worse this dust lingers for quite a while. On my site you can see some of this wood dust from back when the pyramids were built.

Anyhow, that is a brief overview of what the problem is, but for it to make more sense, we also need to understand the magnitudes. OSHA tested hundreds of shops and determined woodworkers make on average roughly 3 pounds of airborne dust out of every twenty pounds of sawdust. By definition airborne dust is dust which does not settle very quickly in normal room air and tends to vanish without a trace when vented outside. Typical airborne dust is sized 30-microns and smaller, but that most dangerous 10-micron and smaller stuff still makes up roughly 1 pound out of every twenty. Roughly one third of the airborne dust we make is this “fine” dust which gets by our natural protections. Worse, it only takes a concentration of about 0.1 mg per cubic meter to pose a medical health risk.

I bought an expensive set of meters and proved to myself that we generate lots of fine dust even when doing woodworking operations by hand that we tend to think of as pretty clean. For instance, my large 3-car garage sized shop failed all the different air quality tests after hand sawing less than seven inches of 1x4 Douglas fir, our most common home framing wood. Even my hand plane when making long spiral shavings generated lots of fine dust.. My power tools make the fine dust by the pound yet a couple of thimblefuls cause a serious problem.

Ok, so that identifies the problem and how little it takes to greatly increase our health risk, but what does it take to collect this fine dust? If we are able to afford some of the new Fein, Festool and other new generation of hand tools that completely enclose the dust generation, we can get great pickup with just about any good commercial grade vacuum. In fact, about the only way to get collection on many portable and hand held tools is to use a vacuum simply because we cannot practically connect a larger dust collector. Unfortunately, even the best Festool router for instance will spray the fine dust all over just as do most of our larger stationary tools. This is why I firmly say that if we don’t start by doing some tool hood upgrades, we are pretty much wasting our time as we will not capture the fine dust.

The only way to control the dust with tools that spray is to come up with better hoods that block all the direct air streams, then build a low pressure area around the working portion of our tools ample to create enough air speed so normal room air currents do not disperse the dust before it can be collected. Without the right hoods and ample airflow the dust will escape collection. It then spreads so quickly that there is zero chance of an air cleaner reducing the airborne dust level quickly enough to avoid failing all the different air quality tests.

This is also why we need a much bigger blower than we need for simple “chip collection” meaning getting the visible sawdust and chips that pose a fire and injury dangers. How much air must be moved for good fine dust collection is something most of our small shop vendors really do not want to acknowledge. The problem is air behaves according to a simple formula where FPM=CFM/Area and air pulled by a vacuum comes from all directions at once so its air speed will fall off at roughly 4*Pi*r*r. As soon as our dust collection air speed drops much below 50 FPM normal room air currents will blow the fine dust away before it can be collected. Testing shows we need upwards of a 15” diameter sphere of low pressure air moving at over 50 FPM around the working areas of our tools to generate the air speed needed to keep the fine dust from escaping.

If you work through the math we need just about 1000 CFM for good fine dust collection, plus updated hoods, on the same stationary tools that we get good chip collection with just 350 CFM. Digging through the literature and physics on blower design and our material handling impellers need at least 3.0 hp with normal ducting overheads. Add the overhead of a cyclone and that overhead jumps to 3.5 hp minimum for good fine dust collection at most small shop stationary tools. The hand tools need either used outdoors or in a containment area with a pretty good equivalent of a big downdraft table.

Okay, so that catches the dust, but how do we get rid of it? We can just blow 30-micron and finer particles outdoors and they will dissipate without a trace a fairly short distance from our discharge. At the same time I would not want to direct the output from my shop at a nearby neighbor’s home which then means doing some filtering.

Filtering is a mess because we have two different standards that apply to the identical filter. A woodworking filter is considered to only be used outside because of the fire and explosion risks. As a result woodworking filters are measured based upon the working resistance that they tend to develop as they season. They season as the filter traps fine dust in the pores that does not come out with normal machine shaking type filter cleaning. These trapped particles increase filter efficiency roughly 10 to 20 fold depending upon how aggressively the filters are cleaned. Filter makers give the “fully seasoned” rating as that also gives how much resistance the filter will cause. A clean new filter has much less resistance, but it will freely pass particles 10 to 20 times larger than a fully seasoned filter.

With a vacuum cleaner that typically operates at over 100 inches of pressure, meaning will push a column of water up over 100 inches, this seasoning is not that big of a deal. We can simply use a very fine filter and the vacuum pushes the air hard enough that it will overcome a fairly high filter resistance.

The opposite is the case with dust collection systems as they generally operate at a pressure below 10 water column (W.C.) inches. Adding five inches or more back pressure will all but kill the airflow we need to pickup the fine dust in the first place. Many have build water and oil filtered based air cleaning systems, but for these to be successful with fine wood dust we need a blower than can push air through the pressure of a number of inches of water. Our typical dust collector and cyclone blowers just don’t have enough power. The vacuums have plenty of power which is why the Rainbow vacuum has a great cleaning system. Regardless, that leaves us having to filter.

When we have to filter we can simply look up or use a vendor supplied formula which uses air volume and dust loading to tell us the total filter area we need for a given fineness of filter. At typical wood dust all synthetic filter loadings we can get by nicely with a typical 30-micron open dust bag with only about 25 square feet of filter area, but when we drop to 10-micron filters we need about one square foot of filter for every 10 CFM. Dropping further to 1-micron filters means we need about one square foot of filter for every 4 CFM of airflow. A 0.5-micron filter needs one square foot of filter area for every 2 CFM of airflow. But if you read the top filter maker product literature closely they recommend doubling their minimum area recommendations as that will quadruple the filter life and allow four times as long between cleanings. That is important because cleaning can soon ruin filters. Additionally, we must double that again if we use a paper and synthetic blended filter as they are not quite as efficient and generate more resistance. As far as the HEPA filter goes, that is just a term that means each filter has been individually tested and is given a unique certification number guaranteeing that the filter will provide 99.97% efficiency on filtering particles 0.3-microns and larger.

Anyhow, all of this leads to a problem and explains why I came up with the solution I recommend. The problem is simple, a 1000 CFM wood dust filled airflow needs 1000 to 2000 square feet of filter area and filters are expensive ranging up to $1 per square foot depending upon filter fineness, plus overloading and over cleaning both quickly ruin filters. We need to pre filter to bring the dust level down enough to keep from having to buy and constantly replace expensive fine filters. If we pre filter using coarser filters we add to what is already too much back pressure and kill our needed airflow. A cyclone separator seems to be the simplest solution, but when I started my efforts a decade ago the best woodworking cyclones passed close to 100% of the fine filter clogging/destroying dust. I came up with a filter that provides five times better fine dust separation permitting using much smaller filters. I still recommend using 600 square feet of filter with my cyclone design.

Anyhow, that is the condensed digest version. I hope it helps with this thread.

Bill

Originally Posted by mic-d

The need for a clean room is so that you can run a controlled experiment to determine the efficiency of your filter. You need somehow to have a room or chamber without any dust that you charge with exhaust from your machine, whereupon that air is analysed by various detectors to determine the particle size and density of dust not being trapped by your filter. If you cannot do that, you cannot make a single claim about the efficiency of your filter. Do you not see that?
Again, please explain how you to make a wet cyclone that is more efficient than the industrial scrubbers (for which I quoted figures of efficiency) they are inefficient on particles below 5micron and a good hepa/PFC prefilter will remove most of the particles down to one micron, of the dust that is collected.
Cheers
Michael

Thanks Mic,
I have a portable Carbon Monoxide meter because as I said earlier, I collapse because of CO in the field caused by 2-stroke lawn Mower.
I do not now have a clean room nor do I think that is necessary. It is easy to make a clean gloved box if all I need is to measure some exhaust. One of the Bro. who attends our prayer meeting and stays 10 mins away, has sophisticated portable Gas & particle analyser but I still think we are off the objective.
As I said, I was trying to copy the "Venturi Scrubber" Design. That design is reported to be even effective for sub-micron particles.
e.g. http://www.scielo.br/pdf/mr/v8n2/a16v8n2.pdf

I do not want to deviate from my objective. I am not going to write a scientific report.
If people want to question "wet scubbers", they should also question cyclones efficiency (see attached).

My background was chemical/biochemical engineering so of cause I do just not talk of "duct counts & dust sizes". I also had been a factory manager for 15 years.

If a cyclone system drives a lot of air outdoor, CO & pollen dust are going to come in with the replacement air. These are toxic & irritants as well.

Best regards.

Crikey, even Bill can't get the term HEPA right.

The term HEPA does not refer to a specific efficiency and micron rating.

HEPA or any filter for that matter can be made to any specification.
One can buy professionally rated HEPAs or filters that are rated at
- 99.5% of particles at 1 micron or larger.
- 99.95% of particles at 0.5 microns or larger
- 99.97% of particles at 0.3 microns or larger
- 99.97% of particles at 0.1 microns or larger
- 99.997% of particles at 0.3 microns or larger
- 99.9997% of particles at 0.3 microns or larger
- 99.9997% of particles at 0.1 microns or larger
ETC

A full filter specification includes
- efficiency ie % capture
- at a specific micron rating (actually its for a range of micron ratings)
- a nominal operational pressure drop
- a surface area and flow rate
- a construction material description
- and a partridge in a pear tree

There is nothing magical about the 99.97% of particles at 0.3 microns or larger. Total amount of air, particle density and air flow rates have to be factored into the situation. If this type of filter is used to one pass filter mega cubic metres of air with a bazzlion particles per cubic metre it may be more dangerous than a 99.5% filter filtering a few cubic metres of air with a zillion particles per cubic metre (a zillion being much less than a bazillion).

If you think about micron sized particles, then what about the home vacuum cleaner? Have you ever thought about the micron sized particles venting into your home?

Clean as shop, polluted air while watching TV

Originally Posted by woodie2

If you think about micron sized particles, then what about the home vacuum cleaner? Have you ever thought about the micron sized particles venting into your home?

Clean as shop, polluted air while watching TV

Common Vacuum Bags & filters are 5 micron class.
For some Brands filters can be ungraded.
In the house, I have a VAX canister (TOP model) and VAX sells the "HEPA cartride filter" aftermarket at about $55 at their warehouse at bayswater Victoria.
I found that out when I wrote in the warranty card remark that fine dust was spewing out of the outlet.

I like ShopVAC better. Basic Vacuum is cheap. But They have dry wall filter bags 95% at 0.1 Micron and drywall class Cartridge filter. They also have HEPA filter cartridge 99.97 down to 0.3 micron. Their Cartride and Bags are larger so can last longer. All can be obtained via special order (e.g. via Bunnings). Can also be bought at their warehouse in Hallam Victoria but price at Hallam could be higher. For the Workshop a Minicyclone such as the Clear-Vue mini cyclone connected before ShopVAC can reduce the cost of buying filters.

Thanks you Bill Pentz for such a detailed contribution to our forum - glad to see you are a member - and look forward to further contributions.

It has been quite difficult to sort our the fairly simple basic science and engineering from the myths and confusion created by marketing propaganda. I, for one, are starting to feel comfortable with the concepts.

Originally Posted by BobL

Crikey, even Bill can't get the term HEPA right.

The term HEPA does not refer to a specific efficiency and micron rating.

HEPA or any filter for that matter can be made to any specification.
One can buy professionally rated HEPAs or filters that are rated at
- 99.5% of particles at 1 micron or larger.
- 99.95% of particles at 0.5 microns or larger
- 99.97% of particles at 0.3 microns or larger
...............ETC

Easy, Bobl. There may be quality control rules on the other side of the Pacific. If something doesn't filter 99.97% at 0.3 micron then it should not be called HEPA, but the marketers say that burgers & chips are good for you and smoking does nott cause ......

From my perspective, this has been a great thread. Lets keep it focused and relevant.

Cheers

Graeme

The US Institute of Environmental Sciences and Technology, IEST-RP-CC001.3 and US MIL-STD-282 Method 102.9.1, both say a HEPA filter must capture a minimum of 99.97% of contaminants at 0.3 microns in size.
The 0.3 micron benchmark is used in efficiency ratings, because it approximates the most difficult particle size for a filter to capture. HEPA filters are even more efficient in removing particles that are smaller than 0.3 microns and larger than 0.3 microns.
So “99.97% at 0.3 micron” has become the assumed “DEFACTO MINIMUM STD” whenever the term “HEPA” is used without explicit specifications.

HEPA is an acronym which stands for “High Efficiency Particulate Air” of course can have other specs. but vendors are expected to clearly specify them if they really have something better (or worse) to sell. e.g. Gore is a reputable Filter Maker for Vacuum Cleaners Made/Designed in USA, does not use HEPA for their CleanStream Filter but only on their Cleanstream Pro Filter.
• GORE™ CleanStream® Universal Replacement Filters for ShopVac® Wet-Dry vacuums
GORE™ CleanStream® Filters trap dirt on the surface – just tap or rinse to clean – dirt and debris is removed from the filter. Filters pick up either wet or dry – no need to remove filter when used for water leaks, wet basement, plumbing emergencies and spills

• CleanStream Dry Vac Filter

Works Great for Dry Applications
High Efficiency (=”not HEPA”) 99.7% efficient at 0.3 microns

• CleanStream Pro Wet/Dry Vac Filter

Works Great for Wet Applications
HEPA - Traps Fine Dust 99.97% efficient at 0.3 microns

I would only buy Cleanstream Pro for my ShopVac if I am looking for HEPA filtration not Cleanstream without the pro.

Lets get real.
There are all sorts of typical woodworker
When & How does a hugh cyclone solution fit in?

1. Scrollsaw Hobbyist. Has sroll Saw + small Drill Press + hand tools.
2. Minature Woodtuner (e.g. Pen Turner)
3. Woodturner. Lathe + Band Saw +
4. Beginner Woodworker. Makes furniture with a Portable Circular Saw + a Router (table/portable)
5. Triton User. Has 9-1/4” Circular Saw mounted on Triton WorkCenter. Has router table too.
6. Richer Hobbyist. Just traded in Triton workcenter for a Stationary Table saw.
7. Professional + Serious Hobbyist. Has all sorts of stationary Workworking machinery.


For 6 and 7 of course.
So for 1 up to 5, there must be alternative solutions since if "fine dust" is real problem ALL are afected.

Originally Posted by reuelt

Lets get real.
There are all sorts of typical woodworker
When & How does a hugh cyclone solution fit in?

1. Scrollsaw Hobbyist. Has sroll Saw + small Drill Press + hand tools.
2. Minature Woodtuner (e.g. Pen Turner)
3. Woodturner. Lathe + Band Saw +
4. Beginner Woodworker. Makes furniture with a Portable Circular Saw + a Router (table/portable)
5. Triton User. Has 9-1/4” Circular Saw mounted on Triton WorkCenter. Has router table too.
6. Richer Hobbyist. Just traded in Triton workcenter for a Stationary Table saw.
7. Professional + Serious Hobbyist. Has all sorts of stationary Workworking machinery.


For 6 and 7 of course.
So for 1 up to 5, there must be alternative solutions since if "fine dust" is real problem ALL are afected.

Reueit,

Your numbers 1, 2 and 3 are almost always at the most risk from fine wood dust exposure. These are the ones who most often choose to work with the more toxic woods and often foolishly work inside their homes. A couple of thimblefuls of fine dust, less than we would make cutting just 7” of 1x4 with a hand saw, scroll sawing about 28” of ¼” thick wood, or turning and sanding a typical pen blank will make far more fine airborne dust than OSHA, EPA, etc. will allow in a large two car garage sized shop. Since the silica portions of this dust lasts thousands of years, frequently adding to a contaminated area rapidly builds up so much fine invisible dust that just walking around stirs up enough dust to peg many air quality meters. Wearing a mask while working inside is worthless because once the mask comes off, we end up with an ongoing residual dust exposure.

In my case, I never worked inside my home but did work inside my garage based shop, mostly doing scroll sawing. There is a self closing door between the garage and home. About the only dust that could get into my home either came through that door when it was being used or was carried on my shop apron, clothes, skin, hair, etc. when I went in and out. Three months after I stopped woodworking, my certified air quality inspector found my home air contained over ten times the allowable ACGIH factory air quality standard which is over 100 times the EPA recommendation. A microscopic examination showed most was wood dust. Worse, that dust contained lots of cocobolo, and just about every other toxic wood I regularly used. I was lucky that the rest of my family also did not get sick.

Your numbers 4, 5, and 6 are pretty safe if they wear a good approved dual cartridge mask when making fine dust and do their woodworking outside or in a garage based shop that always has a strong fan blowing outside a side door with the main door cracked. The fan will blow away almost all of the fine dust in anywhere from twenty minutes to an hour.

The high end hobbyist or professional needs much better dust collection to allow them to spend far more hours in their shop without always having to wear a mask. They can get by when they put and vent their dust collection system outside and use a strong fan again with good ventilation.

Alternatively, in areas where location (neighbors) or weather (too hot or too cold) forces working inside a home, shop or garage regardless of your 1 to 7 scale, all need to seriously address fine dust collection. We know from experience that the only things which work are upgrading hoods to block the fast moving air streams then moving enough air to capture the fine dust before it escapes followed by getting rid of that captured dust. A good air cleaner will pull the airborne dust level down enough to keep us from seeing any problems and save our finishes, but those of us with meters have found air cleanres are not effective at getting rid of the finer invisible dust known to cause the most problems. Even if these air cleaners are upgraded with finer filters which constantly clog, it still takes them hours to reduce the airborne dust level amply to pass an air quality inspection. That means we need either a dust collector or cyclone. The physics are pretty simple, moving ample air to pull in the fine dust even from a scroll saw requires around 1000 CFM. To move that much air given filter and ducting resistance we really need a 3 hp motor turning a 14” diameter material handling impeller at 3450 RPM powering our dust collector. If we add the overhead of a cyclone, even my efficient design that still requires at least a 15” impeller turned by no less than a 3.5 hp motor. Other cyclone designs simply pass the fine stuff right through and most vendors sell claimed 1-micron filters that ASHRAE rates as 10-micron filters.

So yes there are lots of solutions other than buying or building a cyclone, but it is still up to each woodworker to learn the dangers of fine dust, make sure they have checked a good toxicity table, and then take ample precautions. For example, although my doctors banned me from my shop (soon to change I hope) my daughter still loves to do some woodworking, mostly art projects and making special gifts for friends and family. She prefers to work outside and wears her 3M 7500 series fitted mask when making fine dust. When the weather is bad she uses my dust collection system, plus works with the garage door open a little and a fan blowing out the side door. Even at freezing temperatures she is comfortable using our three heat dishes.

bill

Originally Posted by bill pentz

Reueit,

Your numbers 1, 2 and 3 are almost always at the most risk from fine wood dust exposure. These are the ones who most often choose to work with the more toxic woods and often foolishly work inside their homes. A couple of thimblefuls of fine dust, less than we would make cutting just 7” of 1x4 with a hand saw, scroll sawing about 28” of ¼” thick wood, or turning and sanding a typical pen blank will make far more fine airborne dust than OSHA, EPA, etc. will allow in a large two car garage sized shop. Since the silica portions of this dust lasts thousands of years, frequently adding to a contaminated area rapidly builds up so much fine invisible dust that just walking around stirs up enough dust to peg many air quality meters. Wearing a mask while working inside is worthless because once the mask comes off, we end up with an ongoing residual dust exposure.

In my case, I never worked inside my home but did work inside my garage based shop, mostly doing scroll sawing. There is a self closing door between the garage and home. About the only dust that could get into my home either came through that door when it was being used or was carried on my shop apron, clothes, skin, hair, etc. when I went in and out. Three months after I stopped woodworking, my certified air quality inspector found my home air contained over ten times the allowable ACGIH factory air quality standard which is over 100 times the EPA recommendation. A microscopic examination showed most was wood dust. Worse, that dust contained lots of cocobolo, and just about every other toxic wood I regularly used. I was lucky that the rest of my family also did not get sick.

Your numbers 4, 5, and 6 are pretty safe if they wear a good approved dual cartridge mask when making fine dust and do their woodworking outside or in a garage based shop that always has a strong fan blowing outside a side door with the main door cracked. The fan will blow away almost all of the fine dust in anywhere from twenty minutes to an hour.

The high end hobbyist or professional needs much better dust collection to allow them to spend far more hours in their shop without always having to wear a mask. They can get by when they put and vent their dust collection system outside and use a strong fan again with good ventilation.

Alternatively, in areas where location (neighbors) or weather (too hot or too cold) forces working inside a home, shop or garage regardless of your 1 to 7 scale, all need to seriously address fine dust collection. We know from experience that the only things which work are upgrading hoods to block the fast moving air streams then moving enough air to capture the fine dust before it escapes followed by getting rid of that captured dust. A good air cleaner will pull the airborne dust level down enough to keep us from seeing any problems and save our finishes, but those of us with meters have found air cleanres are not effective at getting rid of the finer invisible dust known to cause the most problems. Even if these air cleaners are upgraded with finer filters which constantly clog, it still takes them hours to reduce the airborne dust level amply to pass an air quality inspection. That means we need either a dust collector or cyclone. The physics are pretty simple, moving ample air to pull in the fine dust even from a scroll saw requires around 1000 CFM. To move that much air given filter and ducting resistance we really need a 3 hp motor turning a 14” diameter material handling impeller at 3450 RPM powering our dust collector. If we add the overhead of a cyclone, even my efficient design that still requires at least a 15” impeller turned by no less than a 3.5 hp motor. Other cyclone designs simply pass the fine stuff right through and most vendors sell claimed 1-micron filters that ASHRAE rates as 10-micron filters.

So yes there are lots of solutions other than buying or building a cyclone, but it is still up to each woodworker to learn the dangers of fine dust, make sure they have checked a good toxicity table, and then take ample precautions. For example, although my doctors banned me from my shop (soon to change I hope) my daughter still loves to do some woodworking, mostly art projects and making special gifts for friends and family. She prefers to work outside and wears her 3M 7500 series fitted mask when making fine dust. When the weather is bad she uses my dust collection system, plus works with the garage door open a little and a fan blowing out the side door. Even at freezing temperatures she is comfortable using our three heat dishes.

bill

Thank Bill.
Let's talk cordially since I am only concerned with Safety and Health and have no other ulterior motives.
1. I agree to try to solve the fine dust problem. (even though my view may be wrong or silly)
2. I do not dispute your calculations or physics
3. I admit that after all the hot "exchanges" of opinions as the result of this thread that suction need to be adquate to suck in fine dusts.
4. But let us not behave like Dr. An WANG who thought/assumed that the only word processor will be the Wang Minicomputer system. (if you understand what I mean).
5. The reason I am trying to use a SHOPVAC with dry filter + "wet filter" is so that air can be recirculated. (I have enough cash in the bank & ZERO debt).
6. More than 1 Shop-VACs will be used.
7. Based on 5, I will be using the output of filtered air connected into specially designed tubes as sort of "air curtain & director" to make sure that the fine dust will be "block from flying everywhere but directed towards the what you would called 'indequate' suction port.
I think as engineer you can understand that a fan blows well but the back of the fan will not suck well.
8. The capacity of a SHOP-VAC filter bag is small so a mini cyclone like clear vue mini before shopvac would help to increase capacity. 2-1/2" (64mm) ports are feasible with Shop VACs.
9. I still believe water will help since I do not like breathing in Formaldehyde from MDF. Dry cyclones cannot remove formaldehyde.
10. Almost all 1 to 5 tools have only 1-1/2" (38mm) or smaller vacuum ports.

If my experiment for my own use works, hobbyist type 1 to 5 may benefit.
It's for safety and health & not for making money.

Thanks for reading.

(N.B. Do not buy ShopVACs models that cannot blow)

Hi Reuelt,
I like your determination in finding another alternative to dust extraction. If you do succeed in making something, I still feel that there will dust floating in your workshop and one will need to either use a room air filtration unit or have a fan that extracts the room air to the outside. I use dust extractors with most equipment and am considering the exhaust fan option. A fan could be mounted in either the wall/window or in the ceiling. If its in the ceiling then the exhaust would be released above the house and better dispersed. Do you have any thoughts on this?

Zelk

Originally Posted by zelk

Hi Reuelt,
I like your determination in finding another alternative to dust extraction. If you do succeed in making something, I still feel that there will dust floating in your workshop and one will need to either use a room air filtration unit or have a fan that extracts the room air to the outside. I use dust extractors with most equipment and am considering the exhaust fan option. A fan could be mounted in either the wall/window or in the ceiling. If its in the ceiling then the exhaust would be released above the house and better dispersed. Do you have any thoughts on this?

Zelk

An exhaust fan or chimney would help if it is hot air. It may help to bring in air from the door or window.
But fine dust is a different problem. It is held in the air (floating) by electrostatic charges.
We need to catch them at the source.
I have stopped using my belt and palm sander. I now use the bend sender only to sharpen tools.
I have stopped using my lathe. Until I can find some way to capture the dust at source.
As Bill pointed 1000CFM suction draft hood may be required. But that is if you use only suction. 100% correct.
But haven't we forgotten something about "air curtains" principles. Air from top and suction at bottom? They use that for aircond and clean-rooms entrances.
That is what I am basically trying to do. Air-curtain for Sanding station, Air-curtains for lathe so that dust gets into the suction port.
If you think about it, a scoll sawler will benefit, a triton user could benefit - of course if and only if the air curtains jets are done properly.



Best regards.

Reuelt,

I've included some brief comments in blue.

bill

Originally Posted by reuelt

Thank Bill.
Let's talk cordially since I am only concerned with Safety and Health and have no other ulterior motives.Are you implying that I have been other than cordial or have some other agenda? I chose to ignore your digs where you started this thread criticizing me: "Bill Pentz and his cyclone research & Clear Vue Cyclone does NOT seem to have any real solution for a typical hobbyist woodworker." You also have said quite a few things to others throughout this thread that are at best inflammatory. I chose to ignore all that and just tried to provide information that can help those who read these pages.

In terms of another agenda, I do get a little advertizing revenue from my web pages, but generally that income is far less than what I spend each year on research. I neither own, control, nor have any other role with Clear Vue Cyclones other than they do pay me a small commission on each in trade for using my design and advertizing their firm on my web pages. Besides, I put up my web pages five years before Clear Vue Cyclones even existed. They are a father/son team who were so pleased with my cyclone design that they asked permission to go into business building these units. I will say that their customer support has been so good that they have built their firm into one of the largest suppliers with thousands of very satisfied customers.

1. I agree to try to solve the fine dust problem. (even though my view may be wrong or silly) The fine dust problem is a very serious issue that nearly cost me my life, so I have dedicated most of my free time for the last ten years trying to improve the state of the art. You are certainly welcome to pitch in and help. I would prefer that you do your homework rather than get your education in this area on a forum.
2. I do not dispute your calculations or physics. Thank you, but these calculations and physics are not mine. That information has been developed and refined by over thirty years of experience by the dust collection industry leaders who guarantee particular air quality levels.
3. I admit that after all the hot "exchanges" of opinions as the result of this thread that suction need to be adequate to suck in fine dusts. I made no hot or negative "exchanges" and have zero interest in doing so. For what it is worth, I again restate the issue. Vacuum suction and airflows only work if you use a tool that totally traps the dust such as a few of the new Fein and Festool products. Otherwise with most tools we instead must block the fast moving airflows with upgraded hoods then provide enough airflow to surround the working areas of most tools amply to generate at least a 50 FPM airspeed to keep normal room air currents from dispersing the fine dust before it can be collected.
4. But let us not behave like Dr. An WANG who thought/assumed that the only word processor will be the Wang Minicomputer system. (if you understand what I mean). And how is this a constructive comment?
5. The reason I am trying to use a SHOPVAC with dry filter + "wet filter" is so that air can be re-circulated. I think a good shop vacuum with upgraded fine filter is a must in most shops simply because too many tools have smaller ports that require the much higher pressures a vacuum generates to pull air through the small passages. These smaller ports and passages act just like a water valve on the lower pressure air moved by dust collectors and cyclones resulting in terrible collection. A good shop vacuum makes an excellent fine dust collector provided you contain all the produced dust and chips. For instance using a Festool saw while sawing on a piece of insulation foam will trap close to 100% of the generated dust so the vacuum works great. Alternatively the same brand routers will throw dust twenty feet or more with their current dust controls. (I have enough cash in the bank & ZERO debt). ?
6. More than 1 Shop-VACs will be used. A small shop vacuum moves about 50 CFM and a big one no more than 150 CFM. To build a “bubble” of air all moving at 50 FPM or faster around the working areas of our traditional tools we need close to 1000 CFM. So yes, you can use multiple shop vacuums meaning six or more big ones.
7. Based on 5, I will be using the output of filtered air connected into specially designed tubes as sort of "air curtain & director" to make sure that the fine dust will be "block from flying everywhere but directed towards the what you would called 'indequate' suction port. A typical 10” power saw blade launches chips, sawdust, and fine dust at about 9000 FPM so you need to mechanically block that flow or provide an even faster airflow or you will quickly fill the air with a dangerously high amount of fine dust. A powerful air curtain with lower return rarely moves air at more than 3000 FPM. Trying to catch or divert a 9000 FPM air stream with a 3000 FPM stream is like a bike trying to catch a car. If you move the curtain far enough away for the air streams to slow, you end up needing a huge blower. In fact, the formula is CFM=FPM*Area, so building a small 3' wide and 3' tall curtain of air that is 4" thick requires a blower that moves about twenty times as much air as a typical shop vacuum. That means you still need mechanical barriers called hoods then a much smaller air curtain might work. If you can come up with better hood collection and containment system, please do so. I average at least two woodworkers a week writing me saying that they have developed serious wood dust related medical problems. Most end up scolding me for not bashing them over the head with a board to get their full attention.
I think as engineer you can understand that a fan blows well but the back of the fan will not suck well. The back of a fan sucks more air than is blown out the front. The problem is unlike the blown air which hangs together for quite a distance, the sucked air comes from all directions at once which is why the airspeed for sucked air falls of at roughly 4*Pi*r*r where r is the distance. For those who don’t follow think about our shop vacuums. On blow we can blow stuff around many feet away, yet on suction we can’t pickup sawdust more than just a few inches from our collection nozzle.
8. The capacity of a SHOP-VAC filter bag is small so a mini cyclone like clear vue mini before shopvac would help to increase capacity. 2-1/2" (64mm) ports are feasible with Shop VACs. That is why I designed that mini cyclone back in 2000 and why Clear Vue sells so many. In fact medical school testing of that design shows without filters that cyclone is 99.9% effective at separating particles 5-microns and larger. Because getting clogged and cleaning filters ruins filters, this separation ability saves lots of money on filters.
9. I still believe water will help since I do not like breathing in Formaldehyde from MDF. Dry cyclones cannot remove formaldehyde. I never said water would not help, only that you have to provide ample pressure to pump the air through the water and you must use fine enough bubbles that the water will trap the chemicals and fine dust. The problem here is a good water filter needs quite a few inches of pressure which is fine with a vacuum, but not with a typical dust collection blower and a vacuum just does not move enough air for most tools to collect the fine dust. The result of running the vacuumed air through a water filter is great separation for what is captured, but what about the other 5/6ths or more that escapes collection? Additionally, I already have a rust problem and pumping lots of very moist air in my shop poses a more serious rust concern. If I built a water mist or bubbler type filter, it would have to go outside.
10. Almost all 1 to 5 tools have only 1-1/2" (38mm) or smaller vacuum ports. Yes most handheld tools do have these smaller port openings. For them I recommend either working outside or using a vacuum, a downdraft table with sides that can be put up to block the fast air streams, and a good mask plus strong a ventilation fan that exhausts the air from your shop.

If my experiment for my own use works, hobbyist type 1 to 5 may benefit.
It's for safety and health & not for making money. I strongly support your doing these kinds of experiments and wish you every success.

Thanks for reading.

(N.B. Do not buy ShopVACs models that cannot blow)

Originally Posted by zelk

Hi Reuelt,
I like your determination in finding another alternative to dust extraction. If you do succeed in making something, I still feel that there will dust floating in your workshop and one will need to either use a room air filtration unit or have a fan that extracts the room air to the outside. I use dust extractors with most equipment and am considering the exhaust fan option. A fan could be mounted in either the wall/window or in the ceiling. If its in the ceiling then the exhaust would be released above the house and better dispersed. Do you have any thoughts on this?

Zelk

I spent a good part of late 2006 and 2007 traveling around and testing air quality in various woodworker shops. Except for a very few shops almost all tested with dangerously high residual dust amounts. The exceptions were those who had a big exhaust fan with good cross ventilation and the few who went to the trouble to upgrade their stationary tool hoods, put their dust collector outside or build a cyclone and use good fine filters, plus also use a good down draft table. So yes, a good exhaust fan like my 30" put in a side door blowing out with the garage door cracked does wonders on keeping down the residual dust problems. Sadly, the air cleaners only seem to be effective at addressing the larger particles which are not as big of a health risk.

bill