Thread: Small shed dust collection, venting and priorities

Trying to push air to remove (especially fine) dust is like herding cats, it goes in the general direction for about a meter and then doubles back on itself.

For venting to act as an effective dust removal mechanism it needs a one way flow - typically a major opening like a door or open window is used as an inlet, and on the opposite wall you have fans that extracts air from the shed/workshop.

The eaves etc don't count for much BUT if you wanted to further direct the air flow I would block those up that on the same wall as the exhaust fans otherwise that air will by-pass the dust.

You need to target between 10 and 20 room air volume changes per hour.
Most consumer level exhaust fans have significantly less than their claimed rating - in that case use 20 room air changes per hour.

Welcome to the forum Andrew.

Ross

Thanks Bob,

I very much appreciate the info and the experience!

So if I round up the space to 6 x 4 x 4, I get 96 m3. Round up again to 100m3.

This exhaust here is spec'd at 800L/s which the converter below assures me is equivalent to 2880m3/h. This will give me the 20x changes, presumably.
Louvered Wall Exhaust Fan 400MM 16 | Fanmaster

Convert Liter/second to Cubic Meter/hour

For a location, I am considering the opposite wall to the door as per your post. Height will be above head height. Say 3m. Would that make sense?

Extractor Location.png

I also have an option to put an additional, smaller extractor in the closed off window detailed in the floor plan. Is there any value in this or would it be more likely to disrupt air flow or just not do much?

Final thought is, I don't know what I don't know. Are there other questions I should be asking?
ie would two lower powered fans side by side be a better option that a single fan? From an airflow persective.

Many thanks again!

Originally Posted by old1955

Welcome to the forum Andrew.

Ross

Thanks Ross, long time lurker on the forum, first time poster. : )

Hi Andrew, I have a similar size shed to you, 6x9 and I share common thread that it's tool small and never big enough!
Certainly a respirator is a good idea however it may become difficult and a distraction in hot weather. There is a good guide which I followed in that i purchased a DC and located on a small shed adjoining the main shed and purchased second hand PVC pipe for ducting. Really happy with the results and I don't feel I need a respirator other than for spraying organic compound finishes.

Thanks Tom,

I've come to the same conclusion regarding the ducting and DC. Appreciate your insight.
I have it on the list now to do effectively what you said. However, to free up the space, I need to evict my chickens from behind the shed, build a new run/tractor for them, source materials for the ducting, procure and install the DC, install the enclosure etc. To do that I want to finish my new workbench. Oh, and go to work, look after the kids and maybe in the distant future, actually produce something out of the shed instead of upgrades FOR the shed. : )
Money and time go in, currently nothing comes out. Not even dust, ironically.

I think I'll proceed with an extractor for now. I think it will still form part of my dust control strategy to complement a DC and ducting.
The respirator is not so much of a chore for me as it is also a full face shield. Honestly, on a hot day, the positive air flow is quite comfortable.

Fan looks good (more comments below) but I doubt the air flow specs, but even at half the specs this ial be OK
However, moving the louvres will definitely help - Unless there is a safety issue I recommend removing the louvres on ALL exhaust fans - its surprising how much they stymie teh air flow.
If you are worried about bugs coming in, hang a removable flap or insect screen over the top and remove the screen when in use.

RE: Fan location.
You position for a single fan is pretty good.
That location will create 3 "dead spots" (1, 2, 3) as shown on diagram
Dust removal will be effective inside the envelope of the read lines between the door and less so outside the envelope.
Moving the fan towards A will largely eliminate dead spot 1 and reduce dead spot 2 but increase dead spot are 1
Extractor Location.jpg

Two fans at A and B would eliminate dead spots 1 and 2 and also reduce 3.

I also have an option to put an additional, smaller extractor in the closed off window detailed in the floor plan. Is there any value in this or would it be more likely to disrupt air flow or just not do much?[

This is a really good idea as it will put a big dent in the sizes of dead spots 1 & 2. If you put a fan at the window I would move your current proposed fan position slightly towards B

[

Final thought is, I don't know what I don't know. Are there other questions I should be asking?
ie would two lower powered fans side by side be a better option that a single fan? From an airflow persective.

It won't change air flow much but the next question I would raise is noise.
The fan you propose is a very good fan but it is on the noisy side, 67 dB doesn't sound like much but the lower you can get these the better.
BTW The higher noise level also explains the relatively fast extraction rate.
Those fans also consume 154W

I'm not necessarily recommending these but a budget level solution can be using basic bathroom fan from Bunnings for about $25. They are very quiet (48db) and low power (38W) and claim to move ~350 m^3/hr. Three of these (located at the window and A and B) will give 1050 m^3/hr (throw away the covers) at 114W, plus you don't need to run all 3 at the same time - for general work one will probably do when you are running machines use all 3 and leave them running for some time after you have finished. BTW 3 x 48dB fans will generate about 51db of noise.

A more up market solution are these Hydroponics fans.
4"/5"/6"/8"/10"/12" INLINE CENTRIFUGAL EXHAUST DUCT FAN Blower + Leather Jacket | eBay
They do cost more, but while they are quiet, They do use more power but I guess grow your own people don't usually care about this as they often bypass the power meters !

As you can see there is always a trade off. More fans have advantages but then there's more effort needed with installation.

Welcome to the Forum Andrew and thanks for kicking off with a terrific question. Big thanks also to BobL for providing such thoughtful and useful advice. Even though I have a cyclone DC and a ceiling fan, I still have a fine dust problem, presumably coming from the fine filter canister and also from the table saw. I have been considering installing an extractor fan in one of the windows, so BobL's detailed advice, particularly on the dead zones, is really helpful. I would like to ask in my case the DC is in a corner of a 6x6m shop with windows nearby on both adjoining walls. So would a pair of fans, one in each window, be worthwhile? Cheers Charlie

Originally Posted by CharlieZ

Welcome to the Forum Andrew and thanks for kicking off with a terrific question. Big thanks also to BobL for providing such thoughtful and useful advice. Even though I have a cyclone DC and a ceiling fan, I still have a fine dust problem, presumably coming from the fine filter canister and also from the table saw. I have been considering installing an extractor fan in one of the windows, so BobL's detailed advice, particularly on the dead zones, is really helpful. I would like to ask in my case the DC is in a corner of a 6x6m shop with windows nearby on both adjoining walls. So would a pair of fans, one in each window, be worthwhile? Cheers Charlie

Residual fine dust will usually be stuff that escapes collection in the first place and leaks in the DC. The latter is best fixed by enclosing the DC and venting the enclosure outside the shed.

Escaped dust removal is best tackled by improving the dust extraction system eg improving the machinery dust ports and can be assisted by ventilation. Almost any ventilation is better than none.

Exhaust Fan locations.JPG

This is such good information. Thank you, I'm very grateful.


I've added layout and boundaries for context. As you can see, the bulk of the power tools are at the 'B' side. Not sure if that makes much of a difference given the size of the space.
I already have a small bunnings exhaust at 'C'. I will take a hammer to the covers.


Current plan of action is:
- Install a large exhaust at B. Noise is not much of an issue as the tools are pretty loud and there is a large dividing wall well above the height of the fan to the neighbours garage.
- Once I have time and materials in place for a dust collection system, move the exhaust fan to B.
- Install dust collector outside in an enclosure
- Duct inside along side B and to the centre.






I would get the centrifugal fan but I am certain I would end up on a list. : )


Cheers!

Hi all, I'm new to the forum, which i found by lookinf for info just like the above. Many thanks! I've just bought two of these 350mm exhaust fans, 350mm Axial Flow Plate Fan | Fan Warehouse
to install in my shed.
i also have a 2hp DC which i'm about to convert to vent outside. its hooked up to a maslow CNC, and i use it together with a shop vac with a little cyclone separator.
i have a hose into a into a little hopper under the end of my cutting table to try to take away some fine dust and collect the dust from under neath cuts, although not very effective - plan to set that up better with 100mm ducting to mitre saw etc (via a big gulp that can sit behind the mitre saw I also use a shop vac to directly attach to smaller ports on routers, mitre saw and circular saw
the shop vac i'm sure sends up a cloud of invisible dust so i plan to build a box for it to sit in outside, with just a vac hose port and power lead through the wall to inside.
dust has been bothering me more and more (couple times coughing at night) since i started working in the shed and the exhaust fans are the next step. i now wear a mask 100% of the time in there untill ive got this sorted!!
the shed is a 5x6m gable, with a 3mx 6m lean to off one side - the main door is central to the gable and can stay open 90% of the time as air intake.
i'm intending to put one fan up near apex of gable opposite the door, and the other one one on the far side wall, near where i do most cutting..
The shed volume is 150m3, so according to the stats i should get about 32 ACH with both fans going.
i guess i'll figure out dead spots as i go - the diagram you made BobL was super helpful to understand where they might form.
appreciate any other advice or experience setting these up - as well as modifications for DCs to vent outside
cheers, and thanks!
Chris

Good to see you making progress.

Some general comments

The Axial fan you refer to claims 41 cubic meters per hour but I seriously doubt it will do this - most manufacturers claim much more than reality.
A more likely flow will be about half that but at 16 room air changes per hour that will still be plenty.
Using two fans means when you are not actually making dust and just want to maintain some ventilation you can reduce the noise by turning one off.
Those fans will also run on light switch dimmers so you could drop the speeds as required a bit more by using these. They will probably only run in the top 1/4 of the switches range but will still be useful.

Just like locating the vac outside, locating the DC outside is usually better than venting it outside as every time you empty the bags that can spill some dust.

Converting the 2HP DC to make better use of 6" ducting/flex is worth doing - see teh sticky at the top of teh dust forums.

A big gulp behind a mitre saw is better than nothing but a better solution would be a larger shroud/box behind the saw. You will need the DC to be modified to take advantage of this.

Great thread, following along as I'll be doing the same soon. A few questions (probably for BobL - what would we do without mate?)

I've seen these fans also on eBay (

• Silent Extractor Fan 4/6/8" Inch Duct Hydroponic Inline Exhaust Vent Industrial) - slightly less cm3 per hour, but cheaper, quieter, and less power draw. Any reason you recommend the leather jacket ones?

In terms of venting the blower fans outside, is there any use is using a room air filter in addition to/instead of room air changes? Eg, one main fan exhausting outside and then a cheap diy room air filter in the dead spots?

Originally Posted by lemerv

Great thread, following along as I'll be doing the same soon. A few questions (probably for BobL - what would we do without mate?)

Someone else would pop up - they always do.

I've seen these fans also on eBay (

• Silent Extractor Fan 4/6/8" Inch Duct Hydroponic Inline Exhaust Vent Industrial) - slightly less cm3 per hour, but cheaper, quieter, and less power draw. Any reason you recommend the leather jacket ones?

The leatherette jacketed ones are supposedly quieter but I doubt the jacket will make much difference.

In terms of venting the blower fans outside, is there any use is using a room air filter in addition to/instead of room air changes? Eg, one main fan exhausting outside and then a cheap diy room air filter in the dead spots?

Not really, unless you wanted to do some dust free finishing. Remember outside air will always have some dust in it, so turning off exhaust fans and running a RAF will clear more dust from the air.