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Has anyone tested charcoal furnace filters to see if they have an appreciable benefit in indoor air quality?

In commercial settings charcoal filters have been used for years to help eliminate odors and harmful gas particles. While I don't understand the science behind them, charcoal filters attract small gas molecules that would otherwise pass through even a Hepa filter.

I don't know how effective the furnace filters would be, as they can't be overly thick, but I would presume it might work to capture some of the off-gassing polutants? Cartridge style respirators use a rather thin filter and are effective, so who knows. Also, if the charcoal filters are effective, how do you know when they should be changed?

Asked by Rick Van Handel
Posted Mon, 04/28/2014 - 07:55

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6 Answers

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1.
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Rick,
My Google search failed to come up with any reputable, third-party sources of information on charcoal furnace filters.

However, I did find a site that set off my internal scam warning system: one website advertising charcoal furnace filters claims that the product "was originally designed for use in the space program."

For me, that phrase usually means, "Hold on to your wallet and run in the opposite direction."

Answered by Martin Holladay, GBA Advisor
Posted Mon, 04/28/2014 - 08:18

3.
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Martin,

This site has some good info explaining how activated charcoal filters work, but no emperical information available.

http://www.abatement.com/pdf/benefits-of-activated-carbon-filters.pdf

In theory, a carbon filter should help improve indoor air quality. Of interest, is a side note explaining how activated carbon can be used to eliminate VOCs in non vented areas (Similar to how a charcoal canister inside a refrigerator will help reduce odors) If these filters worked, it would be great improvement for new construction, where owners are bombarded by emissions from adhesives, paint, carpet, etc for the first few months of occupation.

Perhaps this is an area that GBA could study in the future? I don't recall an in depth article in FHB that explains why VOCs are bad. I do a lot of reading about green construction and this area seems to be mostly glossed over.

Contractors seem to chuckle about the crazy Californians and there VOC regulations. And they are hesitant to use low VOC products because a lot of the products simply aren't as effective, or at least they weren't as as effective when they first came to market.

Answered by Rick Van Handel
Posted Mon, 04/28/2014 - 09:22

4.
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Rick,
Thanks for the useful link. I agree that it's time for GBA to publish a comprehensive article on VOCs -- good suggestion.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 04/28/2014 - 10:08

5.
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Rick, Here in BC charcoal filters are readily available and extensively used by indoor marijuana grow-ops. If they didn't work we wouldn't have an five billion dollar industry.
Don't forget that until recently range hoods came with a charcoal filter as an option for this who didn't want to vent to the outside. I lived in an house with one for several years and it was remarkably effective.
I'd be very interested in an article on VOC's too. The CMHC has done a lot of research around chemical sensitivities and housing. Well worth a look.

Answered by Malcolm Taylor
Posted Mon, 04/28/2014 - 11:26

6.
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Thanks. I look forward to reading about it in the future.

Answered by Rick Van Handel
Posted Mon, 04/28/2014 - 11:27

7.
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The things I would want to know is how much is removed and how does that improve you health. Also how do you know when it is full.

Activated charcoal is very effective at removing certain pollutants. But how do you know the level of pollutants in the house and how much you can reduce it.

In a carbon filter is added after a furnace filter how does that change air flow i e how restrictive are they. Also it would require running the blower to get the air flow across the filter.

Another question is would a mechanical ventilation system negate the need for charcoal filters,

Lastly there are room air purifiers that run at very low watts compared to a furnace blower. Austin Air makes one with 7.5 lbs of activated charcoal. Would a room air purifier with a large amount of activated charcoal be a better alternative than a furnace filter.

Answered by Robert Hronek
Posted Mon, 05/19/2014 - 12:08

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