If you’re buying a fan, I recommend getting one that does at least 200-250 CFM and is rated for at least 40W. This is what I’m using and it seems okay. You will probably get better results with a more powerful fan. I haven’t looked in too much detail into which fans will handle the pressure difference across the filter well, but my impression is that centrifugal fans are better for this. I will likely replace the fan soon. If you want to estimate how much throughput you need, you can use a copy of this sheet (look at the column ‘Outdoor air exchange rate required for CO2 steady state (m^3/minute)’): https://docs.google.com/spreadsheets/d/1UKNm-DCseQkQ-G-rC1Eiq4_XEq1Sahy7KVyVlh-TseE/edit?usp=sharing
You don’t need to be super meticulous about sealing everything off with tape, except maybe on the parts of the box that are outside. The air pressure pushes the filter against the box, so that helps. I taped the carbon odor filter against the HEPA filter, mainly to give it a bit of protection from larger pieces of stuff outside.
One other perk is that, as assembled, the whole thing makes white noise (or maybe it’s pink noise) that is, to my ear, quite pleasant and good for working or sleeping. It’s a little annoying if I’m trying to listen to something through speakers.
I think I was just trying to match the CFM of my Coway purifier, since I was using the same filters. I was also worried it would be harder to properly mate a larger/heavier fan to a box. Now that I’ve actually built the thing, I would say the larger fan is probably better.
Here are some details that I left out of the main post:
The fan I’m using is this: https://www.amazon.com/gp/product/B01C82SZRM The filter is this: https://www.amazon.com/gp/product/B00C7WMQTW (a bit expensive, but I figured it made sense to buy filters I can use with my commercial purifier, if I they did not work with the homemade one) This is the duct: https://www.amazon.com/gp/product/B07WT519SL
If you’re buying a fan, I recommend getting one that does at least 200-250 CFM and is rated for at least 40W. This is what I’m using and it seems okay. You will probably get better results with a more powerful fan. I haven’t looked in too much detail into which fans will handle the pressure difference across the filter well, but my impression is that centrifugal fans are better for this. I will likely replace the fan soon. If you want to estimate how much throughput you need, you can use a copy of this sheet (look at the column ‘Outdoor air exchange rate required for CO2 steady state (m^3/minute)’): https://docs.google.com/spreadsheets/d/1UKNm-DCseQkQ-G-rC1Eiq4_XEq1Sahy7KVyVlh-TseE/edit?usp=sharing
You don’t need to be super meticulous about sealing everything off with tape, except maybe on the parts of the box that are outside. The air pressure pushes the filter against the box, so that helps. I taped the carbon odor filter against the HEPA filter, mainly to give it a bit of protection from larger pieces of stuff outside.
One other perk is that, as assembled, the whole thing makes white noise (or maybe it’s pink noise) that is, to my ear, quite pleasant and good for working or sleeping. It’s a little annoying if I’m trying to listen to something through speakers.
Why the 6in fan rather than the 8in one? Would seem to move a lot more air for nearly the same price.
I think I was just trying to match the CFM of my Coway purifier, since I was using the same filters. I was also worried it would be harder to properly mate a larger/heavier fan to a box. Now that I’ve actually built the thing, I would say the larger fan is probably better.