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  1. #1
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    Default PM2.5 readings at my local Men's Shed.

    .

    I'm starting this separate thread about PM2.5 readings at my local Men's Shed, as a spin off from my posting #169 in Bob's thread on Developments in Dust Sensor tech...

    During the week I took my first readings, starting inside the cyclone enclosure with the extractor running and the radial arm saw in operation... 1μg/m3, so no dust leakage there.

    There are people living in Delhi who would love to have air anywhere near as clean as that to breathe!

    Some background: Our cyclone was built to Bill Pentz' 3:1 cone ratio design... which doesn't look very familiar as most are built to the squat ratio to fit below low ceiling workshops...

    The cyclone is pulled by a 5HP 3ph motor that only has a 13" impeller (as none larger were obtainable here in Oz at a reasonable cost back then about 15yrs ago). The ducting runs in the shed are all 150mm.

    The port connections to many of the main machines were done while I was absent for a time, so quite a few leave a bit to be desired. But I've been steadily working my way on upgrading those as my time, other duties and energy permit. The radial, drop and bench saws are all now 150mm, as is the snorkel at the wood lathe. The ticknesser only has a 125mm port, so probably next for an upgrade.

    First readings inside the Shed...

    An initial PM2.5 reading at the radial arm saw in use was about 8 μg/m3 and at the 12" bench saw it was closer to 20μg/m3. The radial arm saw is in constant use by particular members, so a focus of concern. A reading of 8μg/m3 is OK'ish and not much above the background readings outside the shed at times.

    But, I would like to get the 20μg/m3 at the bench saw lower and will take some more readings to see how far it gets dispersed and how quickly it drops over time.

    I'll take some more readings this week.
    Stay sharp and stay safe!

    Neil



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  3. #2
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    Very interesting.

    It would be useful to know if it was early or later in the day, and at what height you are taking these readings.
    Also for how long after said activity does the reading stay at the values you report
    Probably the most useful height would be average nose height.

    Also bear in mind that readings below about 10µg/m^2 have about a +/- 100% uncertainty.
    Above that the uncertainty improves but even at about 20 ug/m^3 is can still be +/-50% and above that it may be +/- 20%.
    Even at 20 ug/m^3 I don't think you have much to worry about especially if it is just for a couple of minutes.

    Even if an operator had significant health complications they could sit in 20ug/m^3 for an extended period without a problem.

  4. #3
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    Quote Originally Posted by BobL View Post

    Even if an operator had significant health complications they could sit in 20ug/m^3 for an extended period without a problem.
    Thanks for the input, Bob. I'll will try to keep those parameters in mind when I take some more readings.

    Our latest Shed member is in recovery from lung cancer with one lung removed and the other lung only allowing him to last half a session, so a lower tolerance than most of us.

    But having said that, I'm an asthmatic and also very sensitive to fine dust level exposure. If I get too much during the day I wake up in the early hours of the morning wheezing... I don't need any PM2.5 μg/m3 numbers to know I've had too much.

    In my own workshop I rarely get above 10μg/m3 with the cyclone running and when I do it only lasts for seconds after I stop generating the fine dust. Even if that is actually 20μg/m3, I like to keep it down below there or my lung meter tells me I've had too much. I turn a lot of blackwood and the fine dust from that and some other woods trigger an allergic reaction in my lungs. I would like to get the Men's Shed down to a similar level. They don't use much blackwood, but lots of manufactured boards and recycled timber with all manner of finishes on them that can also be a problem.

    Going by the Australian National Environment Protection Measure for Ambient Air Quality Standard (see below) I would like to get the Shed's PM2.5 readings below 20μg/m3 and ideally down to 10μg/m3 if these economy particle counters can be out by a factor of 2x.

    Table ATM4 National Environment Protection Measure for Ambient Air Quality (Air NEPM), updated 2016
    Pollutant Averaging period Maximum concentration Maximum allowable exceedances (goal)
    PM10 1 day 50 µg/m3 No exceedances (see note)
    PM2.5 1 day 25 µg/m3 20 µg/m3 (2025 goal)
    No exceedances (see note)
    Note: Before 2016, there was an allowance of 5 exceedances per year for the PM standards. This was replaced in 2016 by an exceptional event rule. An exceptional event is a fire or dust occurrence that adversely affects air quality at a particular location, causes an exceedance of 1-day average standards in excess of normal historical fluctuations and background levels; and is directly related to bushfire, jurisdiction-authorised hazard reduction burning or continental-scale windblown dust. The handling of exceptional events in the reporting of averages is specified in the Air NEPM.

    Not that it is my motivating concern, but I wouldn't be surprised if the National Men's Shed Association began to adopt and mandate these exposure levels as a requirement for their member insurance.
    Stay sharp and stay safe!

    Neil



  5. #4
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    The ATM4 AIR NEPM recommendations are average daily exposure standards for outdoor air over 24 hours, so during the day there may often be short spikes that will go well over those levels while at night, especially when general activities like traffic and construction decreases the levels will drop considerably and contribute significantly to a low over average.
    The "maximum allowable exposures" are also for "average daily exposure" so if a levels rise even for several minutes to say 100 ug/m^3 they can still easily meet the standard.
    The ATM4 AIR NEPM recommendations are kept low because that air is what scrubs the crap out our homes and places of work and entertainment etc where it can be significantly higher.

    FWIW in 2016 all Oz major capital cities averaged PM2.5 of between about 6 and 8 ug/m^3 and PM10 of between 16 and 19 ug/m^3. The last PM2.5/PM10 readings I have for the Latrobe valley is for 2014 and they were 10 and 20 ug/m^3.
    Some of the more conspiratorial clean air advocates have suggested that these Oz air standards have been designed to suit the readings rather than the other way around.
    With the more recent bushfires I believe most of these levels have been exceeded by some way, but COVID has brought the levels down again.
    Bush fires and burning off around Perth earlier this year produced about a dozen days of >100 ug/m^3
    To make a significant long term dent in these levels we will have to, start removing all forms of "combustion" including internal combustion vehicles (especially diesels) from our society.

    A more practical set of numbers and "actions", for more immediate exposures is the following chart .
    This one is from the WA Govt Dept of water and Environmental regulation but I believe all the states use a similar recommendations.
    Air quality index - Department of Water and Environmental Regulation
    From this you can see that even a PM2.5 of 50 ug/m^3! is permitted even for sensitive groups, provided they don't develop cough or shortness of breath.

    Screen Shot 2021-11-14 at 9.05.39 am.jpg

    The other thing to bear in mind is that fine dust effects more people from non-breathing related issues than breathing related issues. Like COVID, fine dust has a greater effect on people with co-morbidities, like heart/vascular diseases/conditions, diabetes and kidney problems etc. So you might not feel short of breath or be coughing to be affected. Fine dust is though to be a major cause of strokes especially for people who don't appear to have any other indicators.

    What all of the above fails to take into account is what goes on inside people's houses. Anyone using combustion for cooking or heating especially without any extraction/ventilation, or uses a crappy old vac, or has pets and/or carpets, is likely to experience high particulate levels from time to time. A good old fashioned fry up or roast (without using extraction) can send the PM2.5 levels in our house to over 500 ug/m^3 and thats four rooms away from our kitchen where I keep a particle counter running 24/7. In the kitchen it has got up as high as 1200 ug/m^3 (no extractor) at that level there's no need for a particle detector as there is a decidedly blue haze in the air.

  6. #5
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    Following this thread closely Cheers Barry

  7. #6
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    Quote Originally Posted by mannum3 View Post
    Following this thread closely Cheers Barry
    Took some readings at the Shed on Wednesday, but yet to transfer photos from mobile phone and make some sense of those. Perhaps get to that on weekend.
    Stay sharp and stay safe!

    Neil



  8. #7
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    Now might be a time to show this again.
    Taken in Nov 2017 it shows the PM10 (green) , PM2.5 (red) and PM1 (blue) dust concentrations in ug/m^3 over about a week (tuesday pm to wednesday pm in the following week)
    The gap in th middle is the weekend when the shed is closed (particle counter was turned off).
    Particle counter was turned on in the early morning several hours before members turned up.

    General dust levels are roughly proportional to number of operators - the higher general levels on the friday - was due to a higher morning background and more members attending on friday mornings.
    The spikes are effectively all due to failure to open gates or turn on the DC after say lunch or smoko.


    Screen Shot 2021-11-19 at 8.13.04 am.jpg

  9. #8
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    Bob, thanks for posting those readings for your Men's Shed. That will be useful for comparison and interpretation purposes. As you have pointed out before, the peaks dissipate quickly when the DE system is on and the relevant blast gates are open.

    My counter doesn't record the readings like yours, so I'm just take a snapshots with my mobile phone held at nose height.

    As I never manage to get to the Shed before halfway through the session, I went in and took some readings the afternoon before when there had been no activity there for a number of days.

    First reading outside for a baseline...

    Outside backgroud reading.jpg

    Workshop A
    Workshop A - pre-use.jpg

    Workshop B
    Workshop B - pre-use.jpg

    Workshop C
    Workshop C - pre-use.jpg

    Workshop D
    Workshop D - pre-use.jpg

    So, with just me walking around but no equipment starting up, those are pretty good readings and very similar to the readings that Bob got in the two hours before his Shed fired up.

    Still processing the readings from the next day when the Shed was going. I'll will try to get to those this evening.
    Stay sharp and stay safe!

    Neil



  10. #9
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    Thanks for the readings Neil,

    If a shed is reasonably well sealed and it's not windy or smokey outside its not unusual for PMx readings to be zero µg/m^3.

    This does not mean they are zero it just means they are less than 1.
    Some of my Particle counters can display 0.1ug/m^3 by accumulating data over 30+ seconds.
    At these levels the measurement uncertainties are very high (+/-100%) but the levels are so low they are not worth worrying about

    When a particle counter shows zero µg/m^3 it's interesting to check out the numbers of particles.

    Right now my el-cheap meter and one of my home made meters are side by side in my study and ARE both reading zero µg/m^3 for PM2.5, but the cheap meter is showing around 80 particles/m^3 of 1µm or smaller, whereas the home made meter is showing around 140 particles/m^3

  11. #10
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    The following are some readings I got the following day when the Shed was running.

    Outside background reading was PM2.5 4μg/m3

    15-11 Background.jpg

    Inside the Shed was a different story... a new member had just used the bench saw and he was just closing off the 'snorkel' blast gate and walked off. I asked him would he like me to turn off the other gate for him... he looked puzzled and I realised he thought there was only one gate to open and close for the bench saw...:no:

    Anyway, that gave me a good chance to get some readings after the saw had been used without opening the 150mm blast gate...

    Immediate reading... PM2.5 33μg/m3
    15-11 WS-A benchsaw at 0mins.jpg

    Reading at 2mins... PM2.5 38μg/m3
    15-11 WS-A benchsaw at 2mins.jpg

    Reading at 4mins... PM2.5 17μg/m3
    15-11 WS-A benchsaw at 4mins.jpg

    Reading at 5mins... down to PM2.5 12μg/m3
    15-11 WS-A benchsaw at 5mins.jpg


    So, dropping away over 5mins as expected, BUT at the other end of this workshop I started getting the following...

    Reading at 6mins... up at PM2.5 37μg/m3
    15-11 WS-A benchsaw at 6mins.jpg

    Then at 9mins... down to PM2.5 28μg/m3
    15-11 WS-A benchsaw at 9mins.jpg

    And finally, after 14mins... it got down to PM2.5 8μg/m3
    15-11 WS-A benchsaw at 14mins.jpg

    Failure to open the main blast gate on that table saw illustrated just how far and how long the PM2.5 particles remains in a workspace if not collected at source.

    I'll try next time to get some reading with both blast gates open on the table saw to see what difference that makes.
    Stay sharp and stay safe!

    Neil



  12. #11
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    Thanks for the info Neil, its pretty similar to what I've seen. It would be useful to know how long a machine was in used prior to reading and also approx cut dimensions (workpiece thickness and cut lengths)

    Given the fine dust is scattering to other parts of the shed I'd also be looking at the extraction from the OH guard.

    BTW there's probably no need to post photos of the meter for every reading.
    I doubt any members can read the value on the thumbnails and having to open lost of images to see the values is a bit redundant if teh values are posted in the test
    Listing values side by side or as a vertical list also aids comparisons

  13. #12
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    Quote Originally Posted by BobL View Post
    It would be useful to know how long a machine was in use prior to reading and also approx cut dimensions (workpiece thickness and cut lengths)

    Given the fine dust is scattering to other parts of the shed I'd also be looking at the extraction from the OH guard.

    BTW there's probably no need to post photos of the meter for every reading.
    Yes, I was about to drop the images... it was becoming tedious!

    The OH dust extraction on the table saw is a contentious issue with some Shed members and the readings may help resolve some of that.

    I'll try to capture more info on duration and task, but not always readily recorded by me with members all doing different tasks and often done and gone before I can get from one end of the Shed to the other to do observations and recordings.
    Stay sharp and stay safe!

    Neil



  14. #13
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    A more useful set of numbers on the radial arm saw from today. Readings taken over 30mins run time and cutting pieces (125mm x 35mm cross section) shown in image below at the rate of one every 10 secs...

    Baseline before cutting commenced - 4μg/m3
    Average during 30 mins of cutting - 8-10μg/m3
    Occasional and brief spikes up to - 20μg/m3
    Within 1min of stopping down to - 4μg/m3


    Observing the dust hood in operation over that time ( I don't usually get the time to do that) I thought I could modify it slightly to improve its performance. I will do that and take some further readings after that.
    Stay sharp and stay safe!

    Neil



  15. #14
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    I ran a similar piece of wood through the bench saw (see image below, so about 1m long x 75mm thick) to the one that left so much PM2.5 hanging in the air last time, but with both blast gates open this time!
    Pre-cut reading - 3μg/m3
    Post-cut reading - 33μg/m3
    Within 1min back down to - 3μg/m3

    A much quicker drop, however, an improved OH snorkel arrangement does need to be negotiated to get those 30μg/m3+ readings down, especially for when a big batch of timber is being put through, which happens quite regularly.
    Stay sharp and stay safe!

    Neil



  16. #15
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    Thanks Neil.

    You probably don't need me to say this but any newbies reading this should know that measuring the dust from a couple of cuts or a few minutes use of a machine can be misleading since the fine dust rapidly dilutes into a the shed. Results will differ considerably for longer uses as well as taking much longer to reduce afterwards.

    I saw this at a mens shed where two blokes were turning - thing was they were often pausing and happily chatting away - the dilution of the fine dust was matching their chat pauses. Dust levels never got about 35 µg/m^3 over the half hour I was monitoring them. One other thing they had going was they had super sharp turning tools and there was not a lot of scraping going on.

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