Make up air Filter box for “standard” carbon filters?
BrunoF
| Posted in General Questions on
I am looking to add an inline filter box to my air intake that serves the ERV and the range hood. The range hood can theoretically pull 600 cfm so I want to be sure that I don’t choke it down too much with a filter. We have a commercial composting operation nearby and a few times per month when the wind blows just right it smells like s**t. My main requirement is to be able to remove those odors as much as possible when drawing in fresh air.
I want to size it to use carbon filters that are easily available but I don’t know what size that would be.
any suggestions? Thx!
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Replies
Do you have room to do this on the outside of your house? Any of the typical carbon coated filters will pretty much be a waste of time to take the odour/VOC down. I've been using a carbon canister (used by grow ops) outside to deal with fire smoke, but it works for skunks too. 10" will work fine at 600 CFM. This one has 20lbs of activated carbon: https://terra-bloom.com/products/activated-charcoal-carbon-filter-8-x-24-up-to-750-cfm-1-8-extra-thick-layer-of-top-grade-activated-australian-virgin-charcoal-for-hydroponics-and-growing
I'm using the 8" carbon version in the external cabinet. Pics attached.
Thanks! Unfortunately I won’t have room for something like that outside the house but is there any reason why I couldn’t put one inside the crawlspace?
100% you could put this in your crawlspace by attached a hood/ducting to the open end over the filter. It would be easier to just redo the same concept in a box with a linear layout. I like using these carbon canister filters as the grow industry has made them pretty affordable :-)
The box is MDO 3/4” ply that is sealed on both sides with water base urethane. Taking it inside may require insulation, something I avoided by keeping it outside.
And your sure a 4” carbon filter won’t reduce odors?
It will reduce odours a bit, but that's it. I've tested a few filter setups on my HRV intake and the only one that drops skunk smell, smoke etc. to nearly zero is the larger canister...and this is at 110 CFM max. I've tested:
a. Hood over HRV intake with kitchen type carbon filters - slightly effective for VOC.
b. 14x14x4 carbon coated inline filter - slightly effective for VOC.
c. 4" carbon cartridge filter - too restrictive.
d. 8" Terrabloom cartridge filter - very effective with VOC, low restriction.
It makes sense though when you think in order to react/absorb VOCs the air needs some exposure time to be in contact with activated carbon. In a coated filter there is very little carbon, and even less dwell time. That's why I suggested the 10" filter cartridge from Terrabloom for your application, as a minimum. The 8" filter has about 17lbs of activated carbon...far, far more than a coated filter could possibly contain.
In a furnace, air is recirculated again and again over the same filter so for a period, the carbon will slowly reduce odours, but for make up air, HRV/ERV etc. you only get one pass. The other plus, is that a larger carbon filter should last 1-2 years, depending on flow, so is pretty cost effective. They can also be refilled if you find a cost effective supplier of bulk activated carbon.
My reply was going to be to Google "DennisWood" and you would find your answer; however, Dennis has brought the answer direct to you!!