DIY HEPA Filter: Radial Fan Floor Dryer & Plexiglas

ByJohn Wuethrich

DIY HEPA Filter: Radial Fan Floor Dryer & Plexiglas

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Dedicated single room hepa air purifiers are often expensive with expensive filter replacements. Those units wont dry your entryway, kitchen or bathroom floor after weekly cleaning nor will they do much good in a flood. 

A fairly simple DIY Hepa Filter that moves a lot of air. Its not the cheapest DIY Option but having an Airmover is a good idea regardless of needing or wanting a hepa filter.

I picked this one up from a store in MN called mennards. it was around $200 last year. It apears this is pretty much the same thing at northern tool 

This HEPA Purifier mod would quickly pay for itself used as 24/7 hepa because if you pay attention at big box stores you can often find the 1″ deep filters in clearance. 

Walmarts clearance isle sometimes features 1inch deep Furnace Filters of (high merv value) for $7-$11 a filter a quarter of the size for a dedicated machine can easily run $25 plus.

I think the Air Mover to HEPA Air Purifier I present here is a far better investment. Espicially compared to $200 on a single room dedicated Air Purifier only box. I note in this article that you have 24/48 hrs to get er dry if your house/property/rental takes water damage. 

The velocity and force of this type of fan is by far prefered vs say a box fan. Espicially where carpet is concerned. I seem to remember this coming right from the mold pro but ill see if i can cite it later. 

I will probably do a follow up to this with how to turn a box fan into a cheap hepa unit. the same concept that makes this fail outright(with out one consideration) is often one used scare people away from higher quality filters on hvac systems.


  • Cheaper Filters
  • Hepa Air Purification
  • Dry Floors carpets entryways or wall cavities
  • Runs About same price as a large dedicated Hepa purifier but moves more air
  • Easy To Add Carbon Prefilter, wont be bogged down
  • extension cord with built in double outlet gfci.

Store Hepa

  • Quiet
  • Moves less air
  • no construction invoved
  • cant dry walls, carpets, floors etc.
  • expensive filters
  • single use
  • may or may not allow carbon prefilter

Fan Types and filter requirements

Static Pressure is the reason your hvac installer may recomend against high merv value filters. IIRC above merv 12 is where HEPA starts. The problem isnt actually the merv value so much as it is how thick is the filter. Thick as in deep a 20x25x1 deep is going to have less holes than say a pleated 20x25x5 deep filter. If your furnace can accept deeper filters you can achive better filtration with out aditional strain. I sort of question how much this matters as most furnaces ive seen use blower motors/Radial Fans but i dotn want to get ahead of myself. 

Somewhere along the lines i was introduced to the concept of static pressure. Static Pressure as it applies to this convo is the amount of resistance the fan blades/motor is going to experience as the filter gets more fine. 

there are a ton of videos on youtube where some idot slaps a 1 inch deep merv 14 filter on a box fan and calls it a day. you will move next to 0 air this way and I guarantee your fan will be dead in less than a month if you run it even a few hrs a day. Axial fans do not deal well with static pressure.

Ever notice how if you put something too close on either side of a box fan the sound changes? if you pay attention it stops moving air as well.

Axial Fans

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A huge metal fan and not a guitar or groupie to be seen

This is the oldest type of fan humainty has imagined. A box fan is an example of an axial fan.

I’ll eventually add a way to make a box fan into a reusable decently high cfm hepa air filter. So far I’ve done this 3x but have yet to make a reusable frame (duct tape was required)

Radial Fans

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I need washers i know.

This is the type used in todays/this article. Radial fans are also known as Centrifugal fans, blower fans, and or squirrel cage blower. Its odd to me that in 2020 this technology still carries such a premium but who am I to fight the Nut Gathers

Seriously though; I’d be highly surprised if there isn’t a few designs on thing verse or the like to 3D print everything but the baring and motor for way cheaper. International Union?

radial fans tend to be louder but can generate higher pressure air (relative to that around it) and if one applies a filter or increases the static pressure the fan feels the reduction in air is usually significantly less drastic than the same filter on an axial fan. radial fans deal with static pressure far better

I need to get some washers to put between the screws and the plexi but keep alternating between starvation, mold clean up and wondering if theres going to be a roof over my head while eating a toxic fast food and gas station food diet. This is by far not the cheapest hepa air purifier one can build but it will move a lot of air. While not the cheapest having a floor dryer/air mover isn’t a bad idea for any home or apartment so the value is there if you have a few tools to modify it.

DIY Hepa Filter Air Mover:

im working on a page dedicated to working with plexi time is limited but it will get more complete someday.


  1. Philips screwdriver
  2. assorted drill bits
  3. sheet of plexiglass
  4. methylene chloride (paint stripper)
  5. jigsaw
  6. compound miter saw
  7. 80 tooth harbor freight miter blade
  8. a knife and ruler can be used to score the plexi cuts as well. It’s just more time consuming.
  9. syringe or squirt bottle for paint stripper aplication.
  10. weather stripping
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As you can see above its really just plexi box with hole cut in the center of the bottom. You need to drill carefully and add relief holes before attempting to remove the middle. I use a harbor friend 80tooth 12in blade on my ryobi compound miter. Cutts plexi like butter.

the expensive plexi welding compound you can pick up online? paint stripper is the main ingredient. You need a decdently smooth edge/cut  and you just but them up and run a bead. you can clamp it but you will notice within maybe 30 seconds it will be semi stuck. I tend to clamp for 2 plus hrs. Its at its full strength in about 24.

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