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  1. #1
    Join Date
    May 2009
    Posts
    196

    Media filter odor load up

    Are there any good ways to prevent media filters from loading up with odors and re-releasing them after the original source is gone?

    I've got a media filter setup soaks up any ambient odors--cooking, smoke, paint fumes, nearby skunks, etc--but re-releases them into the air for hours after the original source has been removed.

    I have confirmed the source is the media filter as the removing the filter removes the problem.

    Is this an inherent problem with media filters?

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,803
    Add an activated charcoal air filter to remove odors.
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    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Oct 2009
    Location
    Murfreesboro, TN
    Posts
    108
    The nature of preferential adsorption is that gases will be displaced by a smaller molecule from an adsorptive material. The water molecule is the smallest. Gases are also media specific. Activated carbon is used for high molecular weight VOC such as Ammonia and Urea. Potassium impregnated carbon is used for acid gases SO2, H2S, NOx. Phosphoric Acid impregnated carbon is used for caustic gases. Potassium Permanganate impregnated Aluminosilicate is used for low molecular weight VOCs like Sulfur compounds. Sodium Thiosulfate impregnated Aluminosilicate is used for Chlorine and Chlorine Dioxide. Catalytic Carbon is used for acid gases.

    That is why using a gas phase filter for cigarette smoke requires a mixture of adsorption materials. Depending on who you listen to there are between 4,000 and 6,000 harmful substances in cigerette smoke.

    Another way to reduce inside odors is by dilution using fresh air that is being exchanged by an energy recovery ventilator.
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  4. #4
    Is this a trick question?

    Seems to me that if you captured the odor in the media filter and were concerned about releasing it back into the indoor environment, you would change the filter.

  5. #5
    Join Date
    May 2009
    Posts
    196
    Quote Originally Posted by breathe easy View Post
    Seems to me that if you captured the odor in the media filter and were concerned about releasing it back into the indoor environment, you would change the filter.
    It's not affordable to replace a >$100 media filter cartridge every few days to prevent the HVAC system from smelling of cooking for 4h after dinner.


    Are there activated charcoal filters available for residential use that a) work, and b) cost less than .2" static?

    As far as smell retention is concerned, would I be better off using a traditional 1" disposable filter instead? I'm thinking that normal filters would re-emit odors for less time as they'll capture many fewer odor emitting particles.

  6. #6
    Join Date
    Oct 2009
    Location
    Murfreesboro, TN
    Posts
    108
    A resent study done by the California Energy Commission, Ventilation and Indoor Air Quality in New Homes, said that very few people use natural ventilation, i.e. open a window, or mechanical ventilation, turn on the kitchen exhaust hood, to provide necessary ventilation to control odors and add fresh air. It sounds like that is what you need to do when you cook.

    Open a window and turn on your exhaust hood when you cook and if the hood is vented to the outside you should be good to go. That way you can use a standard filter for the dust and ventilation to capture and remove the cooking odors.

  7. #7
    Ventilation would help. In fact, it is a major way to reduce indoor air pollution. However, keep in mind that an open window and a running ventahood will pull out "conditioned air" from your house at about the rate of the ventahood fan ie. 200-1,600 cfm.

    Many of the thicker media filters come in a carbon media version. What type of media filter are you using?

    A 1" filter would not help. It just adds to your pressure drop from the filter. Assuming the same media you would capture about the same amount of cooking odors.

  8. #8
    Join Date
    May 2009
    Posts
    196
    Quote Originally Posted by breathe easy View Post
    Ventilation would help.
    I can't do much more to increase ventilation. Right now I have a 6" outside air intake connected to the return plenum. The house itself is very leaky to begin with.

    What type of media filter are you using?
    Carrier PerfectAir. There's no carbon variant available and the filter housing is a non-standard size.

    A 1" filter would not help. It just adds to your pressure drop from the filter. Assuming the same media you would capture about the same amount of cooking odors.
    What I'm thinking of is pulling the media filter entirely and using a 1" filter alone. Taking a hit on MERV performance would be worth not having smells linger for days.

    It's also not just cooking but anything that gets into the house: fireplace smoke, incense, paint fumes, etc, etc.

  9. #9
    cf
    If you elect to go with the 1" filter, you could use the carbon media variety. these will adsorb odors and will have much lower restriction than a high MERV 1" filter. You will give up something on the particle efficiency side since these are normally around a MERV 6. But it may help to solve the odor problem.

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