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You can build your own high-flow HEPA filter for about $45: 1x 20-inch box fan ($20) 1x 20x20 MERV-13+ MPR-2400+ HVAC air filter ($20) 1x roll of duct ta
by throwaway984393 5y ago
You can build your own high-flow HEPA filter for about $45:
1x 20-inch box fan ($20)
1x 20x20 MERV-13+ MPR-2400+ HVAC air filter ($20)
1x roll of duct tape ($2.50)
Air particle meters and other testing show they work just as well as big expensive machines (it's just the filter doing all the work). This is indeed a dirt cheap way to improve overall health.
- dragontamer 5y ago> 1x 20x20 MERV-13+ MPR-2400+ HVAC air filter ($20) That's a MERV-13 filter, not a HEPA filter. HEPA filters 99%+ of small (0.3um) particles per pass. A MERV-13 filter only filters like 60% per pass IIRC. That means that a 1000 cu. feet of air through the HEPA filter will result in 990+ cu. feet of clean air. While the MERV-13 filter will only produce 600 cu. feet of clean air. -------- A MERV13 filter would be good enough to improve most air, but its not HEPA and shouldn't be confused with it.
- bsilvereagle 5y agoIt’s worth noting that filter efficiency is a function of particulate size. A MERV13 and a HEPA filter are nearly equivalent for filtering pollen, but have drastically different performance for smoke and virus particles. There’s a plot 1/3 of the way down the page that shows the curves: https://frdmtoplay.com/nagivating-air-purification/ https://frdmtoplay.com/nagivating-air-purification/
- dragontamer 5y agoYeah, it's actually pretty complicated. MERV13 also needs less pressure, and a box fan is bad with pressure. If you stuck a HEPA filter on a box fan, it might only do 100cu feet of airflow. MERV13 is maybe 200. HEPA is designed for higher pressure centrifugal fans. MERV13 is likely the best balance for home made designs
- hammock 5y agoThere is a cubic design that people have been doing with HEPA filters (4 sides and a cardboard bottom) that solves the airflow issue.
- diebeforei485 5y ago"Virus particles" do not float free in the air to spread disease. It's usually mostly salt water aerosols with a few virus particles in them.
- cottager2 5y agoIs that known? I don’t think it’s been conclusively decided whether or not the virus spreads via aerosolized droplets or if it’s truly airborne.
- epgui 5y agoThey certainly can free-float, generally speaking, but SARS-CoV-2 in particular is indeed known to be mostly in droplets and aerosols. Personally, I’d caution not to over-generalize this fact.
- cma 5y agoThe smaller a droplet is, the quicker it evaporates due to increasing surface area ratio.
- throwaway984393 5y agoYou're right, thanks for the clarification, this is a "DIY air purifier" not a "HEPA" filter. (Apparently products today even have to clarify if they are "true HEPA" due to misleading marketing) According to this website (https://freshairaustralia.blogspot.com/2020/01/how-does-merv-13-filter-compare-to-hepa.html https://freshairaustralia.blogspot.com/2020/01/how-does-merv...) a study for underground mining filtration found a MERV-16 filter superior to HEPA in terms of airflow and cost, with a negligible difference in filtration efficiency. According to the study, the MERV-16 filters have higher flow rates than a HEPA filter, which would both make the MERV filter a better fit for an inefficient fan, and increase the air filtration rate. The author of that site also finds that the airflow rate can be more important than a filter's rated efficiency: https://freshairaustralia.blogspot.com/2020/01/why-air-flow-matters-more-than-filter.html https://freshairaustralia.blogspot.com/2020/01/why-air-flow-... After some web searching, it seems you can buy smaller replacement HEPA filters and MERV-16 filters starting at ~$40. So I guess you can spend less if you only need "air purifying", and more if you want the real deal.
- geoduck14 5y agoThis is fascinating! If MERV 13 filters 60% with each pass, can we put 5 in a room to increase the circulation/filtration and eventually get to 99% filtration? Also, I found this article which I found informative. Judge it as you please: https://www.iso-aire.com/blog/what-are-the-differences-between-a-merv-13-and-a-hepa-filter https://www.iso-aire.com/blog/what-are-the-differences-betwe...
- geoduck14 5y agoThis is fascinating! If MERV 13 filters 60% with each pass, can we put 9 in a room to increase the circulation/filtration and eventually get to 99.7% filtration? Does it even work like this? Also, I found this article which I found informative. Judge it as you please: https://www.iso-aire.com/blog/what-are-the-differences-between-a-merv-13-and-a-hepa-filter https://www.iso-aire.com/blog/what-are-the-differences-betwe...
- jph00 5y agoThanks to a higher CADR, it can actually be better than HEPA in practice, if you use 4 filters to create a corsi-rosenthal box, as shown here: https://www.texairfilters.com/its-all-about-the-air-flow-through-the-filter/ https://www.texairfilters.com/its-all-about-the-air-flow-thr...
- clairity 5y agonote that phrase like "600ft³ of clean air" are misleading. filtration drops off rapidly with distance from the air purifier, so the fan would need to be quite oversized for a room to experience relatively even filtration. for most rooms, that wouldn't be comfortable, for both noise and draft reasons. i'm down with air purifiers for indoor particulate matter (i.e., air pollution), but they're not really going to make a dent in covid transmission rates. transmission happens mainly during long face-to-face conversations, which mostly precedes/bypasses room air filtration.
- Bombthecat 5y agoYeah, that's what i dont get.. In germany they plan to filter air in classroom... Classroom are pretty big.. How big do they plan the fan to be?!?
- clairity 5y agoit’s the appearance of doing something that’s more valuable to bureaucrats than solving real, underlying problems and providing genuine leadership (like quelling anxiety and fears rather than stoking them). (central) air filtration can be effective against harmful pollutants, but not really against infectious agents like corona.
- Someone 5y ago> That means that a 1000 cu. feet of air through the HEPA filter will result in 990+ cu. feet of clean air. I would think you’d get very, very close to 1000 cu of cleaner air, with only 1% of the particles of the input. It’s not as if that 1000 cu feet has 1% particles.
- 404mm 5y agoGo with MERV-17 - 20 to achieve HEPA-like filtration.
- walterbell 5y agoAny recommendations on retail sources for MERV-17+ filters?
- pkulak 5y agoI see people post this all the time, but I really don't think an axial fan can pull air through a HEPA-like filter. You need to spend $150 on a real solution. It's really not much, includes the filters, and looks a hell of a lot better to boot.
- tootie 5y agoThis Old House has a really good breakdown on filtration and air volume and have a pretty clever DIY box fan approach using multiple filters. Still costs under $100. The Wirecutter recommended Coway filter is $185 on Amazon. https://youtu.be/aw7fUMhNov8 https://youtu.be/aw7fUMhNov8
- xxpor 5y agoPlus mine has a sensor too, so the fan is only loud when it needs to be.
- asdff 5y agoChinesium HEPA air purifiers are pretty good in my experience too, and just as cheap. My Odec model was $35. It is striking how well they can eliminate even just general odors in the home. If I go on vacation and come back to my home, there is a smell (old building). When I started using these filters and come back after a long period away, there is no smell at all, its amazing. Cooking smells go away much faster too. They look a lot nicer than a big ugly box fan with a filter duct taped to it, are much smaller, and the lowest power setting runs imperceptibly quiet. The only issue is that the fans in these devices are cheaply made and can sometimes become unbalanced and start rattling over time. The low cost makes it easy to replace them, though.
- seanmcdirmid 5y agoThat homemade air filter will, however, be much louder than a newer Swedish blue air.