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I've made one of these, and they do work extremely well, but they're missing one key thing that I now consider vital: Activated Carbon. A HEPA filter is doing

I've made one of these, and they do work extremely well, but they're missing one key thing that I now consider vital: Activated Carbon. A HEPA filter is doing the heavy lifting within any air purifier, it is therefore the most important ingredient. Activated Carbon is well known for removing smells/cents, but it does more than just that: It also neutralizes VOCs and some other gaseous pollutants which can travel through a HEPA filter. This is why I currently have a commercial air filtering solution instead of my box fan + 3M filter, it has suspended Activated Carbon around the HEPA filter fabric. I don't know how I'd achieve that with my box fan solution, and I've not seen anyone else try to address it. Other air purification technologies have safety issues (e.g. ionizers, ozone) or just outright don't work (e.g. UV light inside a channel). HEPA and Activated Carbon have measurable upsides with no downsides aside from their cost. They're the best we have today in spaces occupied by people.

sparker72678 5y ago
A DIY solution would be to get activated carbon that's intended for water filtration (fish tanks, etc). Then add a step that moves the air through the media (put it into a mesh box, or heck even just blow the air down onto the carbon that's sitting in a "dish" or some kind. Certainly not as efficient as a commercial all-in-one solution, but it that's not available to you, it can work. You can even make your own "activated charcoal" but it's a pretty messy and time consuming process.
- malfist 5y ago
  Would activated charcoal for aquarium work thought for gas? We're talking about a significant difference in porosity here. Even going with something like ROX (https://www.bulkreefsupply.com/bulk-premium-rox-0-8-aquarium-carbon.html https://www.bulkreefsupply.com/bulk-premium-rox-0-8-aquarium...) it's going to have much larger pores and much smaller surface area than a carbon coating on a filter
  - sparker72678 5y ago
    Good question. I'm imagining that with a small enough space / large enough quantity of charcoal you'd still get benefits, but it's not like I sat down and tried to do all the math.
dekerta 5y ago
You can find activated carbon filters online (and in many stores). Maybe that would work for a DIY solution? https://www.amazon.com/s?k=activated+carbon+air+filter https://www.amazon.com/s?k=activated+carbon+air+filter
tigen 5y ago
Yeah the activated carbon filter in my commercial purifier is just a sheet that sits in front of the filter. You can buy one and duct tape it to the DIY solution. It has to be vacuumed regularly and eventually replaced. Also there doesn't seem to be any need to worry about sealing the filters as the author's experiments showed, and because the stuff you're filtering is already floating around. It would matter in a vacuum cleaner or some such pollutant-kicking stream.
mastax 5y ago
These filters have activated carbon in them, though probably not very much of it: https://www.amazon.com/Nordic-Pure-20x20x4-Pleated-Furnace/dp/B01JKZD9TO https://www.amazon.com/Nordic-Pure-20x20x4-Pleated-Furnace/d...

sparker72678 5y ago

A DIY solution would be to get activated carbon that's intended for water filtration (fish tanks, etc). Then add a step that moves the air through the media (put it into a mesh box, or heck even just blow the air down onto the carbon that's sitting in a "dish" or some kind. Certainly not as efficient as a commercial all-in-one solution, but it that's not available to you, it can work. You can even make your own "activated charcoal" but it's a pretty messy and time consuming process.

malfist 5y ago
Would activated charcoal for aquarium work thought for gas? We're talking about a significant difference in porosity here. Even going with something like ROX (https://www.bulkreefsupply.com/bulk-premium-rox-0-8-aquarium-carbon.html https://www.bulkreefsupply.com/bulk-premium-rox-0-8-aquarium...) it's going to have much larger pores and much smaller surface area than a carbon coating on a filter
- sparker72678 5y ago
  Good question. I'm imagining that with a small enough space / large enough quantity of charcoal you'd still get benefits, but it's not like I sat down and tried to do all the math.

dekerta 5y ago

You can find activated carbon filters online (and in many stores). Maybe that would work for a DIY solution? https://www.amazon.com/s?k=activated+carbon+air+filter https://www.amazon.com/s?k=activated+carbon+air+filter

tigen 5y ago

Yeah the activated carbon filter in my commercial purifier is just a sheet that sits in front of the filter. You can buy one and duct tape it to the DIY solution. It has to be vacuumed regularly and eventually replaced. Also there doesn't seem to be any need to worry about sealing the filters as the author's experiments showed, and because the stuff you're filtering is already floating around. It would matter in a vacuum cleaner or some such pollutant-kicking stream.

mastax 5y ago

These filters have activated carbon in them, though probably not very much of it: https://www.amazon.com/Nordic-Pure-20x20x4-Pleated-Furnace/dp/B01JKZD9TO https://www.amazon.com/Nordic-Pure-20x20x4-Pleated-Furnace/d...