Workshop Pleated Dust Filter / Activated Carbon VOC Scrubber Test

In this video I am going to follow the example of many sensible DIY YouTuber’s, and make an air dust filter or scrubber. This will be similar to many already built but with one different. I will have a layer of activated carbon in the scrubber to capture VOC’s. I’m not sure if this is going to work with my fan, but I am going to give it a go. Best case scenarios it will capture VOC and dust, worst case just the dust.

So I began by taking apart a high velocity fan that I’ll be using. This is a heavy duty model with 12 inch metal propellers, and a three stage speed switch.

My box or carcass is designed for the primary-filter, so the fan will look a little small in there. I am using an 18 inch square G4 pleated filters which are equivalent to Merve 7-8. They are 2 inches deep and I will be using two at the air inlet. These have a 90% + performance rating according to the European Normalisation Standard, and filter down to a size of 5 micrometer.

To give you a sense of scale 5 micrometres is about the same length of the head of a healthy human sperm, while for our friends across the pond, 5 micrometers is about 1 micrometer smaller than anthrax.

I cut my pieces out for the carcass, and simply screwed them together. I used 18mm ply but it would made more sense to use 12mm to make the unit lighter. I placed the pleated filters into the opening, and screwed some strips of 18mm around the edge.

I know some of you are sick of CNC machines, so here’s some magic instead.

I placed the fan mount into the box and began measuring its location. The motor had some protruding screw so I had to drill a couple holes out from the PLY before fitting this with other screws. I used a couple strips of neoprene rubber under the mount to dampen vibration and noise, but also to lifts the rear of the fan clears from the filter bellow.

After deciding where to install the switch, I drilled several holes using several different sized forstner bits and fitted it in place. This was quite fiddly but I didn’t want to dismantle the box and router it out.

I also installed a gland to neatly hold the power cable. Glands and other bulkhead fittings normally fits on thin metal or plastic material. So I had to carefully drill the ply till I was left with roughly 1-2mm of material to bolt onto.

All the wires were connected using crimps – the go to joining method for those who hate soldering. I used a ring crimp to earth the motor where I filed off some paint, and then cable tied all the wiring into place.

I re-fitted the fan, and screwed the capacitor in place – then hot-glue the switch into position, but later decided to screw a small mending plate behind it to properly prevent it from accidently popping out.

The filters simply fit by being pushed into place. They are snug and I may not need to add anything too this.

I fitted a simple baffle in front of the motor, and turned the fan on – no sparks.

The next stage of this project involved me building an elaborate frame to hold a perforated box that would contain activated carbon.

Activated carbon is used to capture toxic elements from the air – and this would have been an additional measure along with the air filtering plants from a previous video.

I’ll briefly explain what I did and why I think this didn’t work. The fan couldn’t force enough air through the carbon because my filter was 6cm thick, and the material I had sandwiched that between was not sufficiently perforated. The air movement from fans is eccentric and difficultly in forcing air through the exit may have resulted in pushing air from the intake filter.

I tried removing the carbon and using the perforated board but the best solution was to use the original front cage of the fan.

I am going to keep a hold of my 5kg of carbon and try think of a way I can attach a more powerful air mover.

So in the end, I screwed the metal frame onto the baffle, and left it at that. The unit looks pretty good and the air movement seems decent for a unit of this size, although the cage does resonate.

It is roughly 1.6 meters/second at the intake and double that at the outtake. I haven’t decided where to install it yet. I might keep it near the table saw or above the CNC.

Some Examples of Sensible DIY YouTubers:

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