I am trying to come up with a way to clean the air in my one-car garage/DIY-woodshop, removing fine sawdust particles smaller than 1-micron, and thought that maybe one or two Corsi-Rosenthal boxes would do it.

Could the fan orientation be reversed so air is blown into the box, with the filters also reversed so the air flows through them out into the room? Sawdust would then collect on the inside of the filters and disposal would be easier.

What would happen in that scenario if the filters couldn't keep up with the fan? If, say, 2" thick filters didn't have enough air flow and what was needed were 4" thick filters? Could the force of the air from the fan dislodge the dust from the filters? Would "blowback" result, with dust coming back out of the box through the fan?

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    $\begingroup$ Generally the fan will create a static pressure inside the box. If there are gaps around the fan then air will flow rapidly out of the gaps and bring dust with it. So don't leave gaps around the fan. You do want to make sure your filters are not restricting the airflow, just because if they do, the airflow is lower. What you're describing is basically how any vacuum cleaner or wood shop sawdust vacuum works. $\endgroup$ Feb 7, 2023 at 9:32
  • $\begingroup$ Thanks for the reply. My main concern is that the static pressure inside the box would cause dust to flow out around the perimeter of the blades, even if gaps were sealed around the fan frame; that is, dust dislodged from the inside of the filters, not "free" dust that was just brought into the box by the fan. I wouldn't want "puffs" of dust to escape. $\endgroup$
    – Tim
    Feb 9, 2023 at 23:48
  • $\begingroup$ I've never heard of that being a problem, which is not to say it isn't a problem, as I'm not trained in fan-ology. $\endgroup$ Feb 10, 2023 at 11:40
  • $\begingroup$ Well, I'm testing it out but will have to wait a fairly long time before there will be enough dust on the inside of the filters to know whether the fan is dislodging any significant amount of dust from the inside of the filters and sending puffs back out the fan's perimeter. The 20x20x2 MERV13 filters seem to have decent airflow. The air coming out of them causes a strip of paper towel to rise to about the 4 o'clock position and stay aloft. $\endgroup$
    – Tim
    Feb 10, 2023 at 14:13

1 Answer 1


In this link is what you are describing. One could add some legs and add a 5th filter opposite the fan so the static pressur is reduced and less risk of dust escaping the fan blade boundary. I hope this helps, and please update on how the reverse CR Box is performing if possible. Thanks.


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    $\begingroup$ Welcome to Engineering! So as to avoid link-rot, please expand your answer to include the relevant information from the link provided, at least the most essential points. Feel free to quote directly from the source. $\endgroup$
    – Wasabi
    Oct 28, 2023 at 18:38
  • $\begingroup$ Thanks for the idea. So, instead of a cardboard base, put another filter there so that air can escape from the bottom as well. $\endgroup$
    – Tim
    Oct 30, 2023 at 21:16

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