SW09 – Dust in the Workshop

Following on from an earlier article of mine on respiratory safety, I thought it appropriate to discuss some of the fixed systems I use in my shop, which helps negate some of the respiratory threats in the workshop.  I say helps negate, because at the end of the day no system is infallible and it is unlikely (in the extreme) that any typical workshop has dust extraction and air exchange systems strong enough to completely eliminate the dust that is generated.

Before I really get into the topic, I will clarify what sort of sawdust I care about.  Neatness in the workshop is well and fine, but I don’t mind having sawdust (as in shavings) around the place – looks like I do some work occasionally.  That sort of sawdust is not posing a direct risk (ok, there is the fire load risk, but that is for another article) (unless you feel like ingesting some!).  What I really care about is airborne dust – the stuff you can breathe.  This comes in all sorts of sizes, and ability to remain airborne, but I’m sure it is safe to say, the smaller particles pose real risk.  They can remain airborne for ages (hours), and many filter units just don’t filter out the small stuff (sub 5 microns).  (A complete aside – a 5 micron particle is 2 1/2 times larger than the granite block I bought last week is flat! – That is accuracy!)

So, PPE (personal protective equipment) can’t necessarily be eliminated, but you can significantly decrease how much it is needed to protect you from the environment you are creating.

Dust extracting equipment is rarely (if ever) the first thing that gets bought when setting up a workshop – PPE tends to be the starting point, and as it becomes frustrating / forgotten / avoided, the need for fixed systems becomes increasingly apparent.

The next item that gets added is a sawdust collector – a vacuum, or a small HP extractor.  These are used pretty locally to the machine, and moved from one to the next as needed.  Or not.  Unfortunately still, often the extractor is forgotten / ignored when there is a quick job required, and it is too much hassle dealing with all that extra stuff, when you just need a quick cut.

So now onto the more serious stuff.

Whether you go for a larger dust extractor (2HP +) and a fixed ducting system (with blast gates for each machine), or a smaller one that you have to move between machines, that is up to you (and your budget).  What is important (from a safety point of view) is what happens to the air that exits the extractor.  This air is fine dust laden, and poses real risk.

In my shop, I place the dust extractor out of the main shed in a small secondary one, and to me this is a really good option.  It then doesn’t matter how clean the air is then – it isn’t in my breathing space. (As it happens, I still happen to have a pleated filter, but that is another story!)  If you do have the extractor in your shop, then you really want a filter that can take out at least 85% of 1 micron dust, and 99%+ of 5 micron dust.

TruPro 2HP Dust Extractor w Pleated Filter

TruPro 2HP Dust Extractor w Pleated Filter

These machines are primarily for removing shavings, but they do pull a lot of air, and therefore will carry the fine particles away from where they are generated.  It is worth mentioning that a vacuum is a high velocity, low volume system – not great for removing large quantities of shavings, but good (in a localised area) for dust and shaving removal.  A 4″ system is a low pressure/velocity, high volume system.  Great for quantity removal, and although isn’t designed for fine particles, that large amount of low velocity air is well suited for drawing fine airborne particles away.

So that is collection at the source of dust creation.  Where it comes to hand-power tools, decent machines normally have the ability to connect a dust extractor directly to the tool (high velocity, low volume).  No point trying to get a 4″ hose connected to one of those!  Actually, a good time to make another point.  It seems to defy logic, but taking a 4″ pipe and reducing it to 1″ does not dramatically increase the airflow and provide incredible suction.  You actually end up with basically nothing.  Just thought you should know.

There are a number of different machines in the shop, all quite capable of producing fine dust, but the obvious one is of course the sander.  To collect dust from this application, the absolute best solution (in addition to onboard dust collection), is a downdraft table.  What dust escapes the first collection is then drawn down, away from you.  And no, I don’t have one (yet).  Oh, and of course different materials produce different amounts of the various sizes of dust. MDF for example produces huge amounts of airborne dust, and because of the binder (glue) used, it is also very toxic.

Now the other aspect of shop-centric dust collection is the overall air quality.  There are a number of solutions to dynamically improving the air quality.  You can use a fan, blowing past you and towards an open door. You can use an extraction fan (but if you wall mount it, make sure that it is one designed to work mounted vertically – a roof extraction fan (which are MUCH much cheaper) ‘s bearings will not cope well with being used vertically.  Also, you might think of using it to blow fresh air into the shop (diluting down the contaminated air) but of course sucking the contaminated air out of the shop, allowing clean air to be pulled in through all the various openings around the shed is the better option.

Depending on the weather though, it may not be desirable to exchange shop air with the outside world.  (Also, dust laden air might not be so popular with your neighbours…..or their washing!)  Instead, an air filter scrubs the air in the shop.  You need an air filter unit capable of filtering all the air in your shop at least 6 times per hour.

Carbatec Air Filter

Carbatec Air Filter

I have found that it is worth starting the air filter as soon as you get into the shop, as it seems to set up a bit of a revolving current that becomes more effective at clearing the air after about 15 minutes or so of operation.  Given how often it filters the shop air, if I create a real dust cloud, leaving the shed for 10 minutes or so means that a good portion of the shed air will be scrubbed before I get back (at least the stuff around my head!).  These units typically have a timing circuit, so they can be left running for an hour or two after you finish for the day, to ensure any remaining dust is removed, and so it doesn’t settle to be stirred up next time you are in there.  If your shed is anything like mine, this is not an issue! (Or rather it is, but a little amount of airborne dust settling is nothing compared to the dust over the rest of the shop!)

Having one of these units has really improved my workshop’s environment (when I remember to turn it on).  Took me many years to get around to justifying getting one.  But I’m glad I have – it does make a real difference.

2 Responses

  1. How much of this is negated if you work in the (semi-)open air? My ‘workshop’ is under a verandah/awning on the side of the house. Open on 3 sides, roof from 3-3.5m. Makes for a bit more rust on the tools (I was eyeing off your table saw restoration video earlier) but seems to keep the dust moving.

    I’ve got a 2HP dusty for mess collection, but I’ve never noticed any dust cloud hanging around for more than 10 seconds before a faint breeze will take it away.

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