Thread: Dust Concentration Measurements

Below are links to a few open access papers that have examined the hazards of wood dust exposure that have been published over the years.

Cancer and wood dust:

https://www.ncbi.nlm.nih.gov/pubmed/9698991

https://www.ncbi.nlm.nih.gov/pubmed/18289366

https://www.ncbi.nlm.nih.gov/pubmed/6494840


Asthma and wood dust:

https://www.ncbi.nlm.nih.gov/pubmed/18427700

https://www.ncbi.nlm.nih.gov/pubmed/19796200


General hazards of wood dust:

https://www.ncbi.nlm.nih.gov/pubmed/15341004

Hi Bob

If I recall correctly, your sensor is a build your own jobbie?

in your researching, have you come across any retail units with acceptable accuracy ? -- in my particular instance "acceptable" would be +/- 30% when referenced to a "proper" detector. (see below)

I've seen references to an Android / ithingy app that uses a device's inbuilt camera and flash to estimate dust levels, but have not found an actual app.




Why only "acceptable"?
I've recently joined a community workshop in Calgary, largely populated by "geeks" who use the wood shop to make components and cases for other projects.
A prevailing attitude to dust can be summerised by this comment -- "the wood shop bay is already dusty so exhausting a built-in vacuum system (without a HEPA filter) into it shouldn't be a problem."
In the recent past, the group has installed what appears to be a decent cyclone DC, but the inlet pipe is throttled down to 5" within the first metre and a half meaning that the system can really only partly service one machine at a time. This system replaced a "dust control" protocol based around using a broom and compressed air to blow the dust and chips out the back door.

If I wish to have a discussion about dust, I will need some measurements -- but as usual cost to get to the "hey we might have a problem" stage is an issue.

any suggestions?

I think many of us don't to be convinced about the seriousness of wood dust but what perhaps we are not as careful with, are other dusts generated in workshops. Most research on wood dust focuses on Cancer and pulmonary effects probably because these are more easily traced but recently (March this year) following a major worldwide study of exposure to ANY dust, has moved dust from the 8th leading cause of death to the 5th leading cause of death in the world. Dust is now know not only to cause many different cancers but to be a major contributor to cardiovascular diseases leading to strokes and goes some way to explaining why seemingly healthy people still get these diseases.

Anyway rather than references about dust I am hoping this thread would be used more by folks who have or are thinking about getting a dust sensor and reporting their measurements of activities and dust levels.

One thing I forgot to mention above is that the week or so worth of dust data contains about 900,000 data points. These are used to calculate 450,000 concentration points, and then collapsed down further by averaging every 10 points to about 45,000 concentration points and this is how many are on that graph. It represents ~3 concentration points about every 30 seconds plus temperature and humidity data. The CSV file size generated is 8.5Mb.

Originally Posted by ian

Hi Bob
If I recall correctly, your sensor is a build your own jobbie?

Correct.

I actually have 7 dust sensors
One (a Sonoff) is, as described by the manufacturer, a subjective toy with 3 air quality settings.
I have put together 4 quantitative dust measuring systems. 3, using the Plantower 7003 sensor, and a wearable system using the smaller A003 sensor.

In the, Developments in Dust sensor technology thread (Developments in Dust Sensor tech) I speak about a link to an independent comparison of the Plantower sensors including with a professional scientific sensor. see The Plantower PMS5003 and PMS7003 Air Quality Sensor experiment

I have done some independent accuracy testing of the 7003 against a professional ARTI system from Uni and that is also summarised in the developments in dust sensor tech thread. An exhaustive test would take me far longer than I have time for even though I am retired, AND I would need a shed that I could make dusty messes in and I am not prepared to do that in my shed.

My summary is the Plantower is suspect at really low values (who cares), and cannot read above 1000 ppb anyway so it cannot be used to make sensible decisions in a shed, for example that has no dust extraction. You simply cannot shove these sensors directly under a sawdust stream or inside a DC dust - the readings will make no sense and it will kill the sensor.

However it seems to be reliable to about +/-20% in the 10 to 500-700 ppb range which is the cross over range between "supposedly safe" and the lowest of the OHS standards (500 ppb for MDF). If you already have some dust extraction or at least good ventilation in your shed this will allow you to use these sensors and make meaningful changes.

The Plantower sensors are accepted by the world wide Air Quality Monitoring network Provided that at least 3 of them are run simultaneously in the same location and the data is averaged between them. This also helps identified outlier values

in your researching, have you come across any retail units with acceptable accuracy ? -- in my particular instance "acceptable" would be +/- 30% when referenced to a "proper" detector. (see below)

In the developments in Dust sensor technology thread I refer to a sub US$100 PM2.5 detector which measures instantaneous PM2.5 concentration values using a Plantower sensor. The problem with this sensor system is it does not give the necessary PM10 dust levels needed by woodworkers, although you could approximate it by multiplying the PM2.5 data by 2. Again you would run a risk of permanent damage if used in a shed where there is no dust extraction. It would be fine to use with hand tools.

The systems I put together, automatically determines multipoint point smoothing averages for concentrations, and sum the particle counts in batches of 10 to generate "particles per litre" rather than decilitre. The systems also record everything as well as measuring humidity and temperature which is sometimes needed to account for unexpected shifts in the data even though there is no dust evident. This is all outlined in the developments in Dust sensor technology thread.

Canada still uses the same outdated OHS standards as the Brit, US and Australian, 1000 ppb for hard wood and 5000 for softwood.
This is a 1960's standard and does not even consider the increase toxicity of Aussie timbers over northern hemisphere timbers.
I fail to see how these levels are anywhere near safe when the WHO recommends seniors and children stay in doors when the concentrations OF ANY DUST goes above 100 ppb.
Recently we had the major international report telling us that dust in general is now the 5th leading cause of death (up from previously eight) and as wood dust is considered more toxic than general dust there needs to be a revision of OHS levels for industry.
Other health groups recommend lower levels that is accepted by industry and then there's the added problem that different folks will have different tolerances.

People like Bill Pentz have pretty well demonstrate what is needed - it would have been good if he had more dust concentration data to show but someone shoved his very expensive dust counter into a duct containing high velocity sawdust and that was the end of it.

I installed one of my recording dust sensor setups at another local metro men's shed this morning.

There were about a dozen blokes and one blokette present, doing everything from metal turning, hand sanding, thicknessing short pieces of timber for a planter box, and occasional use of a SCMS.
Their belt sander is on wheels and only used outside.
Given the amount of gear they have I would have classed the overall level of activity as medium/light - whatever that might mean.

While I was there I wore my personal dust sensor and spent a bit of time wandering around and standing next to operators to see what the dust levels were.

The Shed is high barn like structure with a double 4m high roller door at one end and regular size windows at the other so pretty good natural ventilation
They are using a ClearVue Max with 9" ducting and then (against my recommendation) using only 4" connects to their machinery.

As soon as I saw this I though, OK - now my dust sensors are going to have a real party in here and was hoping to see some high readings.

The personal sensor did not record anything above 50 ppb, and the other sensor did pick up a short burst of over 100 ppb but after that is was all consistent with the personal sensor of <50 ppb.

I won't make any final judgement until I have seen a weeks worth of data but nevertheless I have to say i was surprised at what I did see.

Bob I know we talked about this in another thread but in our small 6m x 3m workshop, I've also found that trying to measure dust levels around the WS is of almost no value - there is nothing to measure, instead, the area around the head of the operator appears to be the critical location for dust concentrations measurements. I refer to this as the "Operator dust zone" or ODZ in this post. This came about after weeks of testing and is due to the following:

1: Tests indicate the good cross flow ventilation virtually removes all high particle counts "outside" of the ODZ "operator dust zone", dust ejection speed slows as it travels further from the cutting tool, and in our workshop it's caught and carried out of the shed by our strong cross flow air stream.

2: The dust concentration in the ODZ is then determined by the combination of the volume and flow rate of cross flow ventilation and the effectiveness of the dust collection method relative to the ODZ - IE: DC flow rate and hood or pick-up design relative to the dust making machine and the volume, speed and size of ejected material generated by the machine operation.

Sanding appears to be one of the worst causes and that includes hand sanding, I now have that under control.

You mentioned sensitive people, like you, I find that very small levels can affect me, in my case I get almost instant sinus and hay fever congestion if the particle count goes above 30 in the ODZ zone, and that lasts for around 2 hours with just one incident. I can do lathe work, band saw, router table and sanding including the spindle sander and not wear a mask with our cross flow ventilation and modified DC hoods etc. However I have to be careful with hand sanding as I can walk away holding the sand paper, once I leave the DC pick up area I can get an instant reaction from the fine powered dust in the sand paper rising with body heat up to head level, I now do that work with a mask. FYI Pine, MDF and some Ply seem to be the worst at the moment.

So this again correlates with what you touched on in a previous thread, good cross flow, even in a big shed, seems to be right up there with the correct DC installation, likely the two go hand in hand for truly effective dust removal.

Although the above is from out small workshop testing, It's looking like your testing might be similar in some big sheds with good cross flow.

Mike.

Originally Posted by MandJ

Sanding appears to be one of the worst causes and that includes hand sanding, I now have that under control.

Hand sanding with dust control is best done with something like the Festool or Mirka sanding pads.

Couldn't find the local distributor for the Mirka pads but they are available here.

Originally Posted by Bohdan

Hand sanding with dust control is best done with something like the Festool or Mirka sanding pads.

Couldn't find the local distributor for the Mirka pads but they are available here.

I think he means "hand sanding" using "hands and sandpaper" only?

Bob I know we talked about this in another thread but in our small 6m x 3m workshop, I've also found that trying to measure dust levels around the WS is of almost no value - there is nothing to measure, instead, the area around the head of the operator appears to be the critical location for dust concentrations measurements. I refer to this as the "Operator dust zone" or ODZ in this post. This came about after weeks of testing and is due to the following:

I like the idea of and ODZ - it reminds me of a DMZ.

RE:Pine/ply/MDF problems
Sounds like you might have sensitivity to the resin/glue?

I was thinking exactly the same thing about the glue/resin. I purchased a couple of different types of gas / vapour detector modules a few months back and have not got around to testing as yet, not sure at this stage if they will be of and use as they were very low cost, but that for another thread if something actually works.

Thanks Bohdam but Bob is correct, it's just "hands and sandpaper only" and only when I sometimes walk away from the down-draft table or sanding hood with the paper in hand, similar effect if I use a hand saw outside to cut pine or MDF, unless there is a good breeze blowing past me I get an instant reaction. However I don't want to go into details here as it will go off Bobs topic of "Dust concentration measurements" in the various shed environments.

No problem with discussing glue/resin in this thread.
It would be interesting to test if a dust filter/respirator substantially reduces your problem or you have to go to a full organic vapour mask.

The other thing to look at is particle size distribution.
You may be measuring very low or zero concentration for dust but there may still be a lot of dust in the superfine size category.
1 , "10 micron sized" dust particle is equivalent in mass to 1000 "1 micron sized" particles, and 37,000 "0.3 micron sized" particles.

So this again correlates with what you touched on in a previous thread, good cross flow, even in a big shed, seems to be right up there with the correct DC installation, likely the two go hand in hand for truly effective dust removal.Although the above is from out small workshop testing, It's looking like your testing might be similar in some big sheds with good cross flow.

Yep I am really starting to see this. Really large sheds have the added advantage of having a much larger volume for fine dust to diffuse into which dramatically lowers the overall dust concentration by simple dilution. Fine dust has a half residence time in air of around 25 minutes so if dust is generated in short, infrequent, bursts (fairly common in mens sheds) then even sheer dilution will reduce the total dust exposure.

The one activity in most mens sheds which rarely consists of short infrequent bursts is wood turning, and I still have not done anything about this at our mens shed. The lathes are not used much - maybe only a couple of times a week and are on wheels so can be operated outside so they were given low priority. A couple of blokes love the belt sander and will sit on it for longer periods - someone should show then how to use a hand plane. The dust collection on the big belt sander is still not 100% kosher and needs attention.

With most DIY shed being much smaller than Mens sheds I can see this being more of a problem for the DIYer, but how to measure things is still not straightforward.

I use a full organic dual canister vapour mask when using solvents, sprays, glues, cleaning / changing filter bags and manual hand sanding. I can spend hours in the shed using our machines without a mask and not have a problem of any kind, but I have some serious airflow through the 6m length of the 3 x 6 shed. I've purposely raised the dust level in the shed to a very high value, tuning on the cross flow completely drops that back to the outside air count in a about 12 seconds with the end door closed (one huge exit opening at the top of the wall) and around 5 seconds with the door open, outside air count is normally extremely low around here.

I also noted that most machine work we carry out in the workshop also produces short bursts of increased particle counts. I only noticed this when measuring a few meters from the exhaust vent of the external DC housing, but in our case it's very noticeable with bowl turning on the lathe, highest was when fine finish sanding. In the workshop I sometimes see a small increase above background counts at face level, but mostly on the Bandsaw when veneering or small log cutting, sometimes using the belt sander, but never on the lathe.

Originally Posted by MandJ

I use a full organic dual canister vapour mask when using solvents, sprays, glues, cleaning / changing filter bags and manual hand sanding. I can spend hours in the shed using our machines without a mask and not have a problem of any kind, but I have some serious airflow through the 6m length of the 3 x 6 shed.

I'm assuming airflow with the DC?

I've purposely raised the dust level in the shed to a very high value,

What's a high value?

tuning on the cross flow completely drops that back to the outside air count in a about 12 seconds with the end door closed (one huge exit opening at the top of the wall) and around 5 seconds with the door open, outside air count is normally extremely low around here.

What do you mean by cross flow - is that using natural ventilation, the DC or another type of fan?
What it would be worth knowing is size and the natural ventilation airspeed though the "huge exit".

At men's shed the main roller door is 4 m x 3. The air speed with the big Evap AC fan running, varies across the roller opening. It's highest down near the floor and near zero up near the top so its very hard to measure and I have only done a few measurements and get a rough average of ~0.25m/s This equates to about 6000 CFM !

I also noted that most machine work we carry out in the workshop also produces short bursts of increased particle counts. I only noticed this when measuring a few meters from the exhaust vent of the external DC housing, but in our case it's very noticeable with bowl turning on the lathe, highest was when fine finish sanding. In the workshop I sometimes see a small increase above background counts at face level, but mostly on the Bandsaw when veneering or small log cutting, sometimes using the belt sander, but never on the lathe.

Again I am assuming this is with DC on?

Originally Posted by BobL

I'm assuming airflow with the DC?

Yes both on.

What's a high value?

Above head height and away from the machine (belt sander) over 500 @ PM2.5

What do you mean by cross flow - is that using natural ventilation, the DC or another type of fan?
What it would be worth knowing is size and the natural ventilation airspeed though the "huge exit".

Cross flow in the workshop is a variable speed, 600mm diameter, through the wall, 3 blade fan in a steel housing. Exit is a 2.3m x 150mm opening.

We have previously discussed the cons of having a forced fan intake as opposed to the normal fan driven exit with passive intake. However since day one, this low mounted forced intake with high mounted passive exhaust port has proven to be 100% effective. There is not a trace of any WW dust build up on any shelf, wall, ledge or any other surface in this workshop in the past 4 years of operation. I have not measured exit flow across the port, however with fan on high the air is in you face 3m from the exit port with the DC running and all ports open, the internal wooden door (with seals) is quite hard to initially open with the fan running, the air fairly rips through the door opening as it opens, once the door is open enough and the pressure drops then it opens easily. The cross flow fan also makes the manometer move when the lathe DC gate is open (DC not Running). Perhaps the slightly pressured workshop might assist in some small part to the lathe fine dust collection - or maybe not, however there is no way to get a particle count reading above the outside background count anywhere above, down wind, up wind or even sitting the counter on the lathe bed down wind.

At men's shed the main roller door is 4 m x 3. The air speed with the big Evap AC fan running, varies across the roller opening. It's highest down near the floor and near zero up near the top so its very hard to measure and I have only done a few measurements and get a rough average of ~0.25m/s This equates to about 6000 CFM !

Again I am assuming this is with DC on?

Yes DC on, and even with the 1.2m x 2m door open it's like a wind tunnel on high, lot of air flow likely enhanced by the narrow sealed, lined and insulated workshop.

Originally Posted by MandJ

Yes both on.
Above head height and away from the machine (belt sander) over 500 @ PM2.5

Thanks. Good on for doing this.
How long do you leave it at that level?

One reason I'm not prepared to deliberately contaminate my shed to that level is because when metal working I use wet lube/coolant so some of my work surface are damp and tacky and they suck wood dust out of the air like a magnet. In the past I was also not so fussy in using extraction while welding or grinding and when that stuff gets damp it also gets tacky so the MW end of my shed and encroaching well into the WW part of the shed has been covered in a light grey sticky goo. I guess I could cover up those surfaces and try it?

Cross flow in the workshop is a variable speed, 600mm diameter, through the wall, 3 blade fan in a steel housing. Exit is a 2.3m x 150mm opening.

Thanks for that

We have previously discussed the cons of having a forced fan intake as opposed to the normal fan driven exit with passive intake. However since day one, this low mounted forced intake with high mounted passive exhaust port has proven to be 100% effective. There is not a trace of any WW dust build up on any shelf, wall, ledge or any other surface in this workshop in the past 4 years of operation.

That's pretty good - sounds like you have it under control and you run a tidy shop - mine sounds like pig stye in comparison.
It sounds like the vent fan has enough speed to pick up dust from surfaces which is saying something about the air speed.

What speed do you normally run your ventilation fan on?
Whats the noise/dB on the vent fan like?