In the market for a single room HEPA filter or air purifier? Here's a versatile DIY solution using an air mover modified to accept an HVAC/furnace filter.
With the solution you never have to pay for the proprietary HEPA filter again.
Here it's seen with a pre filter /large particulate filter mesh over the filter
Materials Needed:
- Plexiglass sheet
- Plexi welding compound / methylene chloride.
- Fender washers
- Weather stripping
- A HVAC filter
Ideal tools
- A miter or compound miter saw equipped with an 80ish tooth blade
- A jigsaw or sawzall to cut out the inner hole
- A tape measure
- A cordless drill or drill press for the screw holes
Note, washers would be a good idea around the screws. I forgot to grab a pack so I just made sure to pick it up by the handle not the plexi.
Ideas on making it better:
Inlaying a ring/outline of plexi around the bottom sheet butted up to the walls would likely help utilize all or the filters surface area.aka prop the filter off the bottom of the box might increase filter life.
Air Filter Merv Ratings
Cost benefit Analysis
It's a $200 airmover/floor dryer fan from menards modified with a custom plexiglass filter box.
It appears it's on sale at the moment.
benefit to using this type of fan is also that the filter will not have a significant effect on. You won't get the full 1050 CFM stated but it'll probably only drop by 20% if I recall correctly.
The science behind it is this is called a centrifugal fan. Versus an axial fan which would be like a box fan. Centrifugal fans are the same type you use in a blower in an HVAC or in your car. They're known to maintain performance with higher static pressure. Static pressure would be in this case the added load that drying air through the filter places on moving the air.
If you've ever noticed even a screen door is enough to impede a box fan.
One of my next posts will be how to work with plexiglass. It's not much harder than a $15 compound miter saw blade from harbor freight and a bottle of paint stripper. But I'll save that for later.
If you already own the required tools and welding compound (methylene chloride/paint stripper) you're looking at about $20 of plexiglass.
So conceivably you could have what I did above for maybe about $220.
You can also always take the filter out and use it for its design purpose or drying floors or just ventilating a room.
It's not a bad thing to have around.
The benefit of building a filter box on one of these is you can usually find this size filter in Walmart's clearance section for about $10.
There's a universal scale for rating filters and I believe it's around Merv 11 that the HEPA rating comes into play I think this was a merv-14 I'll try to find a close up or link a chart if I can find one.
If you buy a purpose made HEPA filter for small or medium room you're usually looking at between 150 and $250 for the unit and $50 or more for the filter.
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