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Hepa Filter Depth- 12inch vs 6 inch- Any difference?

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#1 Severian



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Posted 08 September 2019 - 03:37 PM

I've been scrounging the threads regarding Flow hoods, specifically for more information surrounding the importance of the depth of a Hepa filter for a LFH,


Found a filter on ebay for 139+ free shipping, with dimensions 24x24x12,



I came across one thread here that I've now lost, that had a debate around whether or not the  12 inch depth vs the smaller 5 7/8 or 6 inches would impede laminar flow due to less resistance- but It didn't seem like there was any clear answer as to whether A, the 12 inch depth is undesireable, or B, if it didnt matter at all besides it taking up more physical space.



Does anyone have a concrete answer around this? 


Seems to me that I could justify a 60$+ discount for that extra 6 inches if that is the major difference between the two.





#2 TVCasualty


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Posted 08 September 2019 - 03:50 PM

The ratings of the filters matter more than their thickness. You need true-HEPA, which is 99.99% efficient at 0.3 microns.


A 12" thick filter sounds like it would be ULPA-rated, which is serious overkill for mycology and requires a bigger and more expensive blower to push air through it.

#3 Severian



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Posted 08 September 2019 - 04:48 PM



I'm finding that there seems to be an abundance of these 24x24x12's , and that their far cheaper than their 24x24x 6 counterparts- Both claiming the 99.99% at .3 microns.




Normally, bigger/more intense= more expensive- I don't know why that wouldn't apply in this case- unless like was stated in that thread I can't find, that the larger filters are actually using  the same amount of surface material stretched over a larger area, and so resistance is actually lessened.

Edited by Severian, 08 September 2019 - 05:00 PM.

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