Step 4: Attach the filter to the fan

Using the duct tape, seal the filter to the face of the fan.
add photos! :( -> :)
Great instructable, useful and simple. I read this and thought "Why didn't I think of this?" I am now:)
Thanks! Always glad when my ideas help someone. - Freed
put the filter on the inlet side of the fan and avoid the air escaping issue...plus you don't have all that dust going through the fan...
Interesting points about filter on front vs back. I made one of these last summer and went with in front because I learned that when the filter was in back, the vortex would actually suck in from near the edges of the front of the box and send large amounts of dust back into the air. I'm sure with modification you could correct this, but the easy fix was to move the filter up front to the exit side of the fan. Any vortex in the back is ultimately drawn back and pushed through the filter in the end. And even though it will burn out the fan motor faster, there is no cleaner fan to start the season than a new one.
Fulldec's got the idea :-) Ducttape to the BACK of the fan. now, the fan doesn't struggle so hard. with the filter in front, there's an increase in pressure inside the fan case, thus the blowback, and added stress. with the back-filter, there's a partial vacume. to compensate, aome air will be sucked in around the edges infront, but blown right back out, by the fan... so you end up with around a 90% filtered, 10% recycled airflow... run the rig for a few hours, and achieve the same results(the law of averages kicks in) Also, if it starts to get dust balls stuck to the filter, but the filter is still good, you can gently vacume the filter, without shutting off your fan :-) Best you're gonna get with this is a reductoin in dust, dander, and mabey some pollens. those pricey electrostatic filters do work, and have the added bonus of being ion generators(remember those?) so you get a "fresh" smell. Your idea would work in tandem with one :-) think of it as a pre-cleaner post-cleaner. and as a final step, spend thousands on a hepa-whole house, air-filtration system. now we're talking space shuttle clean air. of course, if you Don't have allergies, this'll just cut down on the dusting some. :-)
Also, the inflow is not as directional and not as strong for most fans.
Some years ago, I made a similar filtration system, but simpler and quicker. Just turn on a box fan and put a filter on the inlet side of the fan. The fan holds the filter in place. Its easy to see how quickly the filter is loading up. I used the really cheap air filters, not the nice pleated ones, though. Worked great for woodworking dust.
Hey, that is just about the coolest thing ever! I SO need to do that!! Thanks!!
You are welcome. :) - Freed
True, but with the filter on the inlet side of the fan, then all of the crud you pull out of the air is just loosely sitting there on the back side of the fan. It comes off when you brush up against the fan, and if the fan falls over, the stuff gets knocked off of the filter onto the floor. No such problems with the filter on the front of the fan.
why not put the filter on the inlet side of the fan? this solves backflow problem

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