Thread: Dust level measurements / clearvue update

Get one of these for hand sanding. They work brilliantly.
https://www.bestabrasives.com.au/col...s/hand-sanders
I have the larger of the two and as well as being effective in the workshop, I also use it when sanding back joints in plasterboard.
Cheers
Bevan

Originally Posted by Enfield Guy

Get one of these for hand sanding. They work brilliantly.
https://www.bestabrasives.com.au/col...s/hand-sanders
I have the larger of the two and as well as being effective in the workshop, I also use it when sanding back joints in plasterboard.
Cheers
Bevan

Thanks Bevan,

Yeah one of these is on the list. Saw them at the woodshow. In addition to dust collection i also like the ease of the velcro attachment. Thanks.

It's good to se someone reporting any dust measurements - good work and good to see the ClearVue doing well.

However, I'm not sure I would be making any too many claims about safety after just one minute of testing?
Do you intend to measure some long term exposures e.g. levels are from real wood working like a half or full day in the shed.

BTW the current standard the 5 and 1 mg/m³ OHS standards are unfortunately somewhat out of date as they don't take particle sizes into account and neither do they take the toxicity of Australian timbers into account as no one has done the research on this yet.
If the particles are mostly >10 micron then 50mg/m³ of dust may not do much damage whereas if the dust levels 0.5 mg/m³ of PM2.5 it might.

The 5 and 1 mg/m³ OHS standards are based on beech and oak and are nominally considered as PM30.
There are some standards for general air quality which take into consideration particles sizes
•Environment Canada acceptable air quality sets a limit of fine particulate matter of 0.03 ppm (PM10)
•US EPA is 0.15 ppm (PM10) + 0.035 ppm (PM2.5) [24 hours] 0.01 ppm [1 year]
•Medical/European Standard 0.1 ppm for fine (PM10) airborne dust
I have never understood why the general public has more stringent limits that wood workers.

Hi Bob,

If I get the chance to use the meter again at home I'll try to take some more structured as well as longer exposure measurements whilst working on a project that involves a fair bit of work.

One minute was enough to get an indicative feel for which processes created the largest dust hazard but of course a longer duration measurement whilst working on a project would provide a much better assessment of overall safety. These indicative measurements did tell me that I have to work on the hand-tool dust next, as the table saw, thicknesser and band saw seem fine.

I'd finished making a few things recently, so it was good to see that there didn't seem to be much respirable <10 micron dust laying around, as the meter would have picked this up as I did a few 1 min walk-arounds. I even sprayed a few surfaces with compressed air whilst doing so and forcefully waved the door around to stir up dust.

The meter I had measures PM1 PM2.5 PM10, Total, and respirable dust levels and provides breakdowns of each at whatever intervals you designate over a total measurement period. For example you may want summary information every 2 seconds for a 30min measurement. You can download the data into a program which will give you all of the fractions, totals, time-weighted averages, peaks etc. Like I said, I just wanted to get an understanding of the meter, how to use it and what data it can generate as I'll need to have my guys use it for some jobs at work. The fact I measured some stuff at home was a bonus - it was the best, most representative dust producing environment I had available to me.

My understanding is that respirable dust (less than 10 microns and increasingly higher percentage as you get smaller in size) is the most damaging / hazardous as it gets far deeper into the lungs and is not easily processed.

What is the molecular mass of wood dust? I'm not sure how to convert ppm to mg/m^3 without this.

Cheers,

Dom

Originally Posted by DomAU

Hi Bob,

If I get the chance to use the meter again at home I'll try to take some more structured as well as longer exposure measurements whilst working on a project that involves a fair bit of work.

One minute was enough to get an indicative feel for which processes created the largest dust hazard but of course a longer duration measurement whilst working on a project would provide a much better assessment of overall safety. These indicative measurements did tell me that I have to work on the hand-tool dust next, as the table saw, thicknesser and band saw seem fine.

I'd finished making a few things recently, so it was good to see that there didn't seem to be much respirable <10 micron dust laying around, as the meter would have picked this up as I did a few 1 min walk-arounds. I even sprayed a few surfaces with compressed air whilst doing so and forcefully waved the door around to stir up dust.

Its quite difficult to raise that stuff off the floor. It falls out of suspension fairly quickly and seems to stay down.

The meter I had measures PM1 PM2.5 PM10, Total, and respirable dust levels and provides breakdowns of each at whatever intervals you designate over a total measurement period. For example you may want summary information every 2 seconds for a 30min measurement. You can download the data into a program which will give you all of the fractions, totals, time-weighted averages, peaks etc. Like I said, I just wanted to get an understanding of the meter, how to use it and what data it can generate as I'll need to have my guys use it for some jobs at work. The fact I measured some stuff at home was a bonus - it was the best, most representative dust producing environment I had available to me.

Sounds like a good meter, I'd encourage you to report total and at least PM10.

My understanding is that respirable dust (less than 10 microns and increasingly higher percentage as you get smaller in size) is the most damaging / hazardous as it gets far deeper into the lungs and is not easily processed.

Dust between 12 and 5 microns is dangerous because it it is known to produce cancers of the nasal passages and upper throat - the good news about these is that they are relatively rare and only clearly evident is high exposure situations like wood turning.
Dust smaller than 5 microns is though to be responsible mainly for allergic reactions - but lung cancers for example are not know to be cause directly by wood dust.
Allergies and autoimmune like reactions are though to be caused by the finer dust.
As the dust gets smaller it is more likely to be breathed deeper into the lungs but also most of it gets breathed out again.
The reality is that not that much is know about the effects because of the complexity of the interactions.

What is the molecular mass of wood dust? I'm not sure how to convert ppm to mg/m^3 without this.

Wood doesn't have a molecular mass, its a complex mixture of compounds and no two woods are the same.

The ppm is usually "by weight or mass" so all you need to know is the density of a cubic meter of air (which is 1.2 kg/m3 at sea level)
for dust measurements its common to use ppm and mg/m^3 interchangeably.

A little offtopic, but can you tell us a little about the extraction on your thicknesser, DomAU ?

My combo unit has a similar looking hood, and I would love to get a 6" hose onto it, but the hood chokes it down to 4". Did you cut off an existing hood or fabricate a new one?

Great to see some more measurements of extraction effectiveness!

Cheers,

Danny

Originally Posted by rtyuiop

A little offtopic, but can you tell us a little about the extraction on your thicknesser, DomAU ?

My combo unit has a similar looking hood, and I would love to get a 6" hose onto it, but the hood chokes it down to 4".

Unless you have a very powerful DC that hood has to be opened up to 6"
Have a look at this thread to see how I did it
The generic 2HP 10" planer/thicknesser dust control issues

Originally Posted by BobL

I have never understood why the general public has more stringent limits that wood workers.

perhaps because the "general public" is exposed 24/7, while wood workers are only exposed for 40 hours per week.

perhaps because a wood worker's pay includes an element of "danger money" which compensates (for labour law purposes) the wood worker for the increased exposure.

perhaps because there's an element of "choice" in deciding to work wood, and the general public doesn't get to choose the cleanliness of the air they breathe.

perhaps because the people who set the standards are ultimately responsible to politicians and -- in the US at least -- politicians are heavily influenced by industry lobbyists.

Originally Posted by rtyuiop

A little offtopic, but can you tell us a little about the extraction on your thicknesser, DomAU ?

My combo unit has a similar looking hood, and I would love to get a 6" hose onto it, but the hood chokes it down to 4". Did you cut off an existing hood or fabricate a new one?

Great to see some more measurements of extraction effectiveness!

Cheers,

Danny

Hi Danny,

Yeah, I cut the end off mine with an angle grinder. Then I heated up a piece of 150mm PVC with a heat gun and molded it over the guard, then pop-riveted it on. I have some picks somewhere I'll try and find. The cut-off opening is a little shy of 6" but the flow is more than enough. Although it does produce a lot of noise due to the amount of air rushing through the thicknesser; far louder than the actual thicknesser in operation (even cutting). I believe BobL did a far more comprehensive job on his machine but it involved making a whole new shroud out of stainless etc. With the Clearvue I didn't need to do that on mine.

Thanks Bob, DomAU!

My metal working skills aren't up to replacing the whole hood like Bob, so I have been thinking about doing something similar and cutting the end off the existing one - I have a moderately powerful dusty, so I suspect I can get away with it - would be good to get away from the annoying 4" port choking it down!

Originally Posted by ian

perhaps because the "general public" is exposed 24/7, while wood workers are only exposed for 40 hours per week.

By general public I was referring to persons in most other occupations e.g. office workers - also only work 40 hours a week.

Originally Posted by rtyuiop

. . . . I have been thinking about doing something similar and cutting the end off the existing one - I have a moderately powerful dusty, so I suspect I can get away with it - would be good to get away from the annoying 4" port choking it down!

It depends on the particular hood.

On mine, before the air passes out of the 100 mm round port (0.087 sq ft) it has to pass through a 40 x 250 mm rectangle (0.108 sq ft) inside the hood.

Replacing the 100 mm port with a 150 mm (0.196 sq ft) port then makes the limiting factor the cross section of the 0.108 sq ft rectangle.

Although difference between the cross section of the 100mm port and the rectangle is ~25% but it wont translate into a 25% increase in flow because the width of the 40 mm (smallest dimension on the rectangle) will dominate the flow.

On my mod I increased the width of the rectangle to 80 mm (0.216 sq ft) and I measured it drawing 924 cfm, the limit now becomes getting air into the hood.

The other thing that restricts the flow in that hood is the floating baffle inside the hood and i removed mine altogether - if you have enough flow that baffle is not needed.

I think my hood is similar to yours Bob, and I think the first modification I'll make is to remove the baffle as well. The baffle gets sucked into the wrong position in thicknessing mode anyway! I can tape it down to make it work but I think extraction will be improved if I just take it out, and that'll save me some hassle too.

Originally Posted by rtyuiop

I think my hood is similar to yours Bob, and I think the first modification I'll make is to remove the baffle as well. The baffle gets sucked into the wrong position in thicknessing mode anyway! I can tape it down to make it work but I think extraction will be improved if I just take it out, and that'll save me some hassle too.

I tried removing the baffle on the stock hood and found it improved air flow in both modes - improved air flow should automatically pick up more fine dust.
However, it resulted in not quite picking up as many chips in planer mode - see why below
The same applies to my hood, however, provided it does not compromise the operation of the machine I'm not worried about chips.

Below is a picture of the stock hood and my hood side by side.
As well as the restrictive rectangular throat being an issue on the stock hood, the gaps through which the air has to pass immediately above/below the cutters, especially in thicknesser mode, is also a problem
This is why I made the gaps in my hood much wider.

Now look at what will happen if the baffle is removed.
In Thicknesser mode the cutters are located above gap T.
The least restrictive air opening is at P so the air comes pouring in through this large opening and follows the green arrow, as it passes over the cutters below T and does a great job of drawing chips and dust away.

In Planer mode the cutters are located above gap P, but now (without a baffle) more air wants to go via the red arrow which is the least restrictive path and This is why a baffle is used in the stock hood.
However if you have plenty of suck (i.e. a big DC and 6" ducting) this is less of an issue because it pulls away WAY more air and more fine dust although it won't be as successful at pulling chips as it will be in T mode
To improve chip flow in T mode I have considered dropping a piece of sheet metal panel into the T gap but I need to think about it a bit more because the air flow will wants to pull it into the hood.

IMG_6657d.jpg

This serves as a really good example of the misconception machine manufacturers have about air flow around cutters and blades.

To grab the fine dust at source, manufacturers think that hoods have to be tight fitting around blades and cutters, whereas they should be much "gappier" and allow the air to flow around, and even at 90º "past" the cutter.
A High flow past a cutter is very successful at capturing fine dust at source. This works well for routers as well.