The best DIY fume extractor for under $50

[thmjpr]

I've had a few desk type simple fume extractors, they were OK but always got in the way and if I wanted good airflow the loud fan noise would be right in my face. I thought I'd hold off for a proper extractor, but they tend to be large and expensive ($500). Understandable given the performance, but there is a middle-ground here, one thats much better than expected.

What we start off with is a highly rated HEPA grade filter: https://breathequality.com/levoit-core-300-review/


link

This was the largest and cheapest filter I could find. Some other possibilities I looked at:
- Xiaomi air purifier replacement ($23). This one is very large, looks to be decent. But its not available locally, and hard to determine if it has any actual quality ratings to validate its performance. Counterfeit filters may exist as well.
- Blueair 411 replacement ($22). Highly rated company, may be a bit harder to mount to due to flexible nature
- Levoit H132 replacement ($17). Cheap, but probably too small and will cause too much restriction.
- Grow type carbon filter ($35). These clearly have the most carbon of any option, I just wasn't sure of the particulate performance as they have no official ratings. They even sell kits that have everything you'd want.

Components:
- Levoit core 300 HEPA grade filter replacement ($20)
- Aluminum foil dryer vent, 4 inch width ($4)
- 120mm+ fan with good static pressure ($0-25)
- Duct tape, foil tape, or any decent tape ($0-2)
- Scrap cardboard or poster board ($0)
- Scrap three wire power cord ($0)
- 4 screws that will bite into plastic ($0-2)

Optional:
- AC or DC fan controller, if stock fan speed is too loud ($10)

Build:
- Take the round filter and mount a standard 120mm fan in the center of the open end. Can be done easily with some self-tapping type screws, two or four. The fan is blowing into the middle of the filter (yes this means the filter is running in reverse, which will reduce life and efficiency).


- Hook up your AC power cable to the fan, if using 120V I would recommend good insulation and grounding the frame of the fan.
- Adapt the inlet of the fan to the dryer vent (ducting box), with whatever method works for you: cardboard and tape, 3D printed, bent sheet metal, etc. Its not too critical, but leave a bit of space above the fan for good airflow, and tape up any gaps or holes. I made a basic cube shape then cut a circle in the top.


- Now you can place the fan and filter somewhere further away from your work area, freeing up space and resulting in less fan noise. Isolate it with foam or bubble wrap from any hard surfaces to prevent vibration.
- The vent can sit on the desk or better, drop down from above the area you are soldering.



Other ideas:
- Locline can be used, but the diameter of the vacuum loc-line is 2.5" ID, which is not convenient here.


Possible fans:
- https://www.newark.com/nmb-technologies/4715ms-12w-b50-a00/axial-fan-119mm-115vac-250ma/dp/87K2126 41dB 15W 0.31" H2O $17
- https://www.newark.com/multicomp/mc19679/axial-fan-120mm-115vac-180ma/dp/70K8562 48dB 0.30" H2O $15
- https://www.digikey.com/product-detail/en/orion-fans/OA4715-12TB/1053-1072-ND/2620977 44dB 0.37" H2O $15

IMO a 120V/220V fan is convenient as no power supply is needed. They also tend to be super thick and heavy (metal frame), with good static pressure (get 0.30" or better). If you can find a comparable 12V type fan, by all means go for it. But I haven't looked at whats available as I have access to salvaged 120V fans. I am using the first one in the list, noise is OK, nowhere near as bad as the desktop Hakko style "leaf blower" desktop extractors. Performance is very good.

Levoit filter notes:
For the Core 300 filter there are four versions: original, pet, toxin, and mold, with original being the cheapest. Theoretically the 'toxin' version is going to be best, but looking at the photos it looked to be no different. I may buy one in the future and compare it to the 'original' to see if it actually has more carbon inside. For now I've stuffed extra carbon "sheet" filtering in the inside to aid in volatile gas absorption, you could always use it as a prefilter near the inlet. These bulk carbon mats can be bought relatively cheaply, and replaced more often than the main filter.

[thmjpr]

Quick performance test:



- Test A: PCB placed flat on table, PM sensor placed just beside board, so it can capture some of the air flow of the smoke. Note how quickly the level drops back to a normal range.
- Test B: PCB held up off the desk (10cm), closer to the extractor hose. PM sensor placed at the edge of the desk, approximately the location I would normally be breathing in air.

During soldering for test B, there was almost zero smoke detected. Then there is a short bump after I finished and put the iron away, I suspect when the iron exits the air path of the extractor some smoke can escape.