Thread: Sea change - workshop installation

I've just re-read a sticky that I'd thought I'd read before, but obviously didn't take in all that well if I did. In particular, the practical FAQ has a section in it about sound baffling.

For the dense layer I've got 19mm plywood, and it just so happens that we have a spare foam mattress that came out of the 'playroom' which will be perfect for the air trapping layer.

Originally Posted by arniew

The corner construction at left of the mitre station will house the dust extractor. I'd be happy to hear about sound baffling options on that one. I'm intending to vent the extractor through the wall to the outside as most dust and debris will be captured by the cyclone.

The space you have allocated for the CV doesn't look very accessible to me. Both in terms of initial installation, and servicing eg having to get down on hands an knees to get the sawdust bin out. I would forgo the shelf in front (or make it removable) and install a door that is higher than the space you have provided.

I agree with BobL it does look a bit tight. Is the bin going to be a custom built taking up the whole space under the bench?

Originally Posted by Christos

I agree with BobL it does look a bit tight. Is the bin going to be a custom built taking up the whole space under the bench?

The photo doesn’t show the whole panel comes off with a few screws. I’ve not yet worked out how the bin will be configured but im thinking it will be short and deep to fit the vacant space. If it is tall or uses a standard dust bin then the ducting will obscure the window. I’m hoping to avoid that.


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I've been doing a lot of background reading on dust control to keep this new installation on track.

The following two articles are listed in the sticky at the top of this forum, but it took me a while to find them among everything else, so I thought it would be useful to post links again.

Thanks BobL for this one.

And Bill Pentz for this longish but excellent summary of issues and solutions.

One thing I've been puzzling about is the issue of cross ventilation in a workshop to clear residual dust and ensure there is no old dust buildup. Bill Pentz recommends a minimum of 30" industrial fan at the exhaust end of a shop (window or door), with a door open on the opposite side. My shop has a doorway on the prevailing wind side, and one opposite, so I'm thinking of a pedestal fan at the exhaust side like this one on ebay. At times the open door and fan may need to be swapped due to strong northerlys.

Will a fan of the type on ebay do the job adequately?

Originally Posted by arniew

I've been doing a lot of background reading on dust control to keep this new installation on track.

The following two articles are listed in the sticky at the top of this forum, but it took me a while to find them among everything else, so I thought it would be useful to post links again.
Thanks BobL for this one.
And Bill Pentz for this longish but excellent summary of issues and solutions.

One thing I've been puzzling about is the issue of cross ventilation in a workshop to clear residual dust and ensure there is no old dust buildup. Bill Pentz recommends a minimum of 30" industrial fan at the exhaust end of a shop (window or door), with a door open on the opposite side. My shop has a doorway on the prevailing wind side, and one opposite, so I'm thinking of a pedestal fan at the exhaust side like this one on ebay. At times the open door and fan may need to be swapped due to strong northerlys.

Will a fan of the type on ebay do the job adequately?

A "30" fan" descriptor is not that helpful. What needs to be specified is the room changes of air per hour and the levels of dust being generated.

When I set up labs with low levels of acid vapour escaping into the lab (ie much worse than wood dust) to keep the vapours below OHS standards we found we had to use about 30 room air changes per hour. It wouldn't pass any sort of OHS muster these day but interestingly, some 30+ years later when I set up ventilation in my shed (113 m^3) I found that about 40 m^3/min sufficient for "most" dust making activities to keep the dust levels down to what was occurring naturally outside the shed. This equates to about 20 room changes per hour. Because of other factors, eg CO from the gas powered forge etc and I did not want to continuously run my DC I more than doubled the ventilation but again it depends what you are doing.

I'd say 20 room changes per hour will cope with hand tools, most power tools and even small machinery (well maybe not belt sanders). Machinery operations that makes continuous dust like sanders and sandpaper junkie woodturners that have still learned how to sharpen their tools will need more than this if they are in there sheds on a semi continuous basis. If you are only working a few hours a week on dusty stuff and the rest of the time using hand tools or assembly or finishing then 10 room changes per hour may suffice,

Now we come to fans - I have repeated this many times and I should put this into the sticky to save myself doing it so often.

There are basically 3 types of fans usually used for ventilation, Like all air moving gear the manufacturers claims are rarely up to what they claim so you should go for a bt of a safety margin if u have the $$.

Radial fans like the one you refer to.
The include most bathroom and kitchen top extractors and teh industrial fans that BP refers to
These are cheap, noisy, inefficient and mostly bluff and bluster so don't actually move much dust relative to their activity. They move a lot of air from in front and to the sides of the fan - squirt it thru the fan and out to sides again where by it drifts back around to the front again - these fans have to be cowled or funnelled or sealed away from their sides to move air over some distance - in fact all fans do this but radials a perhaps a bit worse than te others.

Impeller fans
These are much more efficient (use less power) and lot quieter than radial fans. Our friends in the "grow your own" industry like these and so many are so the ebay prices are extremely good and they will run 24/7 for years. Open impeller fans are what DCs use so that sawdust does not get caught up in the closed impeller structure - they tend to be noisy but can move a lot fo air and dust. something like these https://www.ebay.com.au/sch/i.html?_...OWER+&_sacat=0

Squirrel cage fans.
These are the quietest and most efficient fans. Unfortunately they are also the most expensive.

I would not rely on any wind - If you get frequent wind direction changes I'd install fans at both ends of the she and use those that are working with prevailing winds - Or vent though the roof so it doesn't matter what the direction is.

You might find this thread useful
Dust extractor and ventilation.

Thanks for those notes and ideas Bob!

I've done some reading on the impeller fans and volume changes per hour.

My shed is 4.04mx7.22mx2.6m or about 75.9m^3

From that I've worked out that the impeller fans that BobL gave a link to will provide roughly these changes of volume per hour:
10" 650CFM => 14 changes
12" 1100CFM => 24.5 changes
6" 440CFM => 9.8 changes

With those results I'm thinking that one 12" fan will be ideal. Any thoughts about that and if there is any advantage using two 6" fans?

Originally Posted by arniew

I've done some reading on the impeller fans and volume changes per hour.

My shed is 4.04mx7.22mx2.6m or about 75.9m^3

From that I've worked out that the impeller fans that BobL gave a link to will provide roughly these changes of volume per hour:
10" 650CFM => 14 changes
12" 1100CFM => 24.5 changes
6" 440CFM => 9.8 changes

With those results I'm thinking that one 12" fan will be ideal. Any thoughts about that and if there is any advantage using two 6" fans?

I realise its more work and $ but two 6" fans separated about 1/4 and 3/4 of the way along a wall will draw air form more of the room than one 12" fan in the middle of the wall as this will take more air from the centre axis of the room.

I also forgot to mention the fact that using room volume and flow rates of fans only actually removes about half the dust - the reason is that on average, as much clean air that comes into the shed is removed as about the same amount of dirty air. So all our flow rates (even mine) have to be halved. 20 RACPH is sort of a target (kinda like 1000CFM is a target for machinery) but 12 RACPH will still remove a lot of dust.

I would DEFINITELY do something about those curtains....

Originally Posted by woodPixel

I would DEFINITELY do something about those curtains....

to paraphrase Oscar Wilde -- either the curtains go or the shed does.

Uh-oh, Arnie,

Looks like its curtains for you

Originally Posted by ian

to paraphrase Oscar Wilde -- either the curtains go or the shed does.

It’s funny but I’ve never taken notice of those curtains before, it’s like they were never there. The house is a 70s child. Lots of retro love here [emoji16]


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Originally Posted by BobL

I realise its more work and $ but two 6" fans separated about 1/4 and 3/4 of the way along a wall will draw air form more of the room than one 12" fan in the middle of the wall as this will take more air from the centre axis of the room.

I also forgot to mention the fact that using room volume and flow rates of fans only actually removes about half the dust - the reason is that on average, as much clean air that comes into the shed is removed as about the same amount of dirty air. So all our flow rates (even mine) have to be halved. 20 RACPH is sort of a target (kinda like 1000CFM is a target for machinery) but 12 RACPH will still remove a lot of dust.

Thanks Bob. I’m inclined to go with two 6” fans in that case. I want to do this once and do it well.


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