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A small HEPA Filter for Positive Pressure Box use


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#1 otto9M9otto

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Posted 02 December 2018 - 05:47 PM

I started with a 6-inch square catch basin. Why doesn’t Lowes show the bottom? Well, I will:

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I had some trouble getting true HEPA filter vacuum bags. One Ebay seller’s description said “HEPA” but the package did not. I returned it. Lesson learned.

 

I then glued in a smaller ABS pipe to the back and some wood pieces in the front to mount the filter using Oatey All Purpose Cement:

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I then cut a square from the HEPA vacuum bag, which was two layers. I first glued the outside layer to the wood using the Oatey stuff (smelly). Epoxy or contact adhesive would have been a better choice. Then, using adhesive from an old glue stick, I attached the delicate HEPA layer. I am hoping that the glue stick adhesive will make future filter replacement easier.
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Then I tested the filter using a small-but-powerful muffin fan. I did not detect any air flow: the filter back pressure was too much. But two ganged muffin fans (one happened to be counter-rotating - a good thing) did produce air flow, but it was too kludgy. So I upgraded to a squirrel-cage blower. I made an adapter using wood. The installed finished assembly works great. By that, I mean that the air flow is what I wanted: not too much or too little.
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Attached Thumbnails

  • catch_basin_rear.JPG
  • HEPA_filter_step_1.jpg
  • HEPA_filter_step_2.jpg
  • HEPA_filter_installed.jpg

Edited by coorsmikey, 03 December 2018 - 02:54 PM.


#2 raymycoto

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Posted 02 December 2018 - 09:25 PM

HEPA filters are always some sort of fan-fold configuration. You don't have enough surface area.

I would use something like this from Home Depot - Shop vac HEPA filter. I bet you can make it fit on the intake. Or maybe you could use part of an N100 filter mask.

 

But if it's on the intake, make sure you have no leaks else you suck unfiltered air.

 

hepa filter.jpg

 

Hey, use some different colors - black letters on grey background - almost invisible. 


Edited by raymycoto, 03 December 2018 - 03:16 AM.

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#3 coorsmikey

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Posted 03 December 2018 - 12:36 AM

Possibly change the title to high efficiency filtered positive pressure box? I don’t understand how it could be a “still air box” with a blower unless the switch was off.

Edited by coorsmikey, 03 December 2018 - 12:37 AM.

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#4 otto9M9otto

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Posted 03 December 2018 - 02:40 PM

I like the constructive criticism and suggestions here. How does one edit a post? My excuse for the font: I created this post when the sun was shining on the monitor.

 

Possibly change the title to high efficiency filtered positive pressure box? I don’t understand how it could be a “still air box” with a blower unless the switch was off.

How can a still air box contain still air while anyone is messing with the contents? Only while such activity is taking place, will the blower be switched on.



#5 coorsmikey

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Posted 03 December 2018 - 03:03 PM

Lol yeah SAB’s seem to more of a fancy sneeze guard than actual Still Air. But they do help prevent particulates from falling on your projects. As long as most of the particulates have settled or been neutralized. A Positive Pressure mostly depend on not letting new particulates in and blowing out the loose ones. A good sanitation of the inside is always helpful.

 

Fixed the font and title, let me know if I need to adjust them at all?


Edited by coorsmikey, 03 December 2018 - 04:27 PM.


#6 otto9M9otto

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Posted 03 December 2018 - 03:20 PM

Thanks, coorsmikey. Aside from the little spelling concern (Positive - not Possitive) I appreciate the help.


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