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  1. #1
    Join Date
    Aug 2003
    Posts
    907

    MERV rating of car cabin air filters?

    Does anyone know the MERV rating of car cabin air filters? I imagine it varies by the brand of the car. If so, which brands provide at least a MERV 11 filter or better yet a HEPA? I'm not interested in a free-standing HEPA inside the car, it will be ineffective due to the constant infiltration of new dust as well as being noisy. Yes, I'm thinking of changing my car just so I can get a cabin air filter -- the one I have now doesn't have a filter and it doesn't seem possible to retrofit one in it.
    -If you won't turn it on then nothing else matters.

  2. #2
    pm
    I have not seen any MERV testing results on cabin air filters.

    By the way there are some very effective and quiet stand-alone HEPA filters for cars. The Amaircare unit is a good choice. It plugs into the cigarette lighter and will provide about 20 air changes per hour.

    Might be a bit cheaper than buying a new car.

  3. #3
    Join Date
    Aug 2003
    Posts
    907
    Quote Originally Posted by breathe easy View Post
    pm
    I have not seen any MERV testing results on cabin air filters.

    By the way there are some very effective and quiet stand-alone HEPA filters for cars. The Amaircare unit is a good choice. It plugs into the cigarette lighter and will provide about 20 air changes per hour.

    Might be a bit cheaper than buying a new car.
    Thanks BreatheEasy. However 20 ACH is completely inadequate for a car.
    See "In-Car Air Pollution: The Hidden Threat to Automobile Drivers" by the International Center For Technology Assessment:

    "the lowest air exchange rate for a vehicle sitting still with the vents set to low was 1.8 air changes per hour (ach)... At 55 miles per hour with the vents set on low, the air exchange rates in the CARB study ranged from 13.5 to 39.0 ach."

    http://www.nanoaction.org/doc/In-car...n%20report.pdf

    For my allergies, I want/need an ACH from a free standing HEPA to be 100 times that of the ACH of the source of contaminated air, or better. So, a free standing HEPA in a car would need to provide >2000 ACH for me to be happy. Even if you knew of one, I wouldn't buy it because of the noise, it would be a tornado! The Amaircare unit is a waste of money for me, and probably for most people as well. The only solution that has a chance of working is a HEPA filter catching things before they are introduced in the passenger cabin, and positively pressurizing the cabin. As I said before, the ACH figures of air filters are meaningless without comparison to the equivalent ACH of the infiltrations or sources of contaminants.
    -If you won't turn it on then nothing else matters.

  4. #4
    Join Date
    May 2006
    Location
    Arlington, TX
    Posts
    107
    Wow, very interesting. I'm curious on this subject as well. There doesn't seem to be any data out there on MERV ratings for these pollen filters, but I'd love to hear more about it if anybody has anything to offer. Thanks.

  5. #5
    Join Date
    Aug 2003
    Posts
    907
    I kept looking and sent questions to Toyota and Ford but got no answer. This must mean that they are nothing to brag about, probably MERV 6 or 7. The omission is glaring and a business opportunity for the right people.


    -The closest thing I found was the statement "Unlike home furnace filters, cabin air filters don’t have MERV ratings". -"Freudenberg Nonwovens, maker of MicronAir filters, intends to include MERV ratings on its packaging, perhaps leading other suppliers to follow suit." I sent a question using their web site, we'll see.
    -If you won't turn it on then nothing else matters.

  6. #6
    As far as I can remember when I changed out the cabin filter in my wifes Chev Equinox it was a Hepa. Some of the other GM vehicles probably have the same quality.

  7. #7
    Join Date
    Aug 2003
    Posts
    907

    Confused

    Quote Originally Posted by Hudson hvac View Post
    As far as I can remember when I changed out the cabin filter in my wifes Chev Equinox it was a Hepa. Some of the other GM vehicles probably have the same quality.
    Thanks Hudson. I can't find any information about it anywhere (gah!). The reason I'm cautious is because sometimes it seems people call a filter "HEPA" just because it's a mini-pleat, but it's not really meeting HEPA standards.
    -If you won't turn it on then nothing else matters.

  8. #8
    Join Date
    May 2006
    Location
    Arlington, TX
    Posts
    107
    Agreed, a HEPA filter is going to have a lot of pressure drop to overcome. I'd love to see manufacturers actually provide this kind of information. Thanks to the interenet, the general public is so much better informed about things like this now days, and you'd think filter makers would respond in kind as they have for residential markets.

  9. #9
    Join Date
    Aug 2003
    Posts
    907

    Update

    Based on the information I got from a kind and helpful manufacturer and some MERV charts, I think most are MERV 8. This is underwhelming considering you get only one chance to remove contaminants, as typically the air is not recirculated through the filter.
    -If you won't turn it on then nothing else matters.

  10. #10
    Join Date
    Mar 2008
    Location
    Atlanta, GA
    Posts
    149
    I think the main engineering reason why cars have cabin air filters is to protect the heater core and evaporator from plugging with dust, and not for air quality, despite what the marketing department may say.

  11. #11
    Join Date
    Aug 2009
    Location
    Jurupa Valley, CA
    Posts
    1,787
    I just think it's funny that the common fix for IAQ in homes is fresh air from outside.. and now you're worried about too much fresh air infiltrating into your car, ruining IAQ.

  12. #12
    Join Date
    Nov 2006
    Location
    Desert Southwest
    Posts
    719
    A shot of lysol in the fresh air cowl intake under the winshield once a week does wonders. The one that smells like fresh linen isn't so harsh. Just run through the different vent cycles after you spray it and let it sit for a few hours.
    If you can't fix it with JB Weld, Duct Tape, and Ty Wire it has to be replaced.
    No good deed goes unpunished.
    If you want to take off friday to go fishing then make sure you train your helper right.

  13. #13
    Join Date
    Aug 2003
    Posts
    907
    Quote Originally Posted by CraziFuzzy View Post
    I just think it's funny that the common fix for IAQ in homes is fresh air from outside.. and now you're worried about too much fresh air infiltrating into your car, ruining IAQ.
    Particulates and gases are two different problems, although both are IAQ concerns. Fresh air dilutes CO2, VOCs and other gaseous pollutants generated inside homes. Highway air has small diesel particles that's been shown to penetrate deep in longs and cause cardiovascular problems. There's also brake, tar and tire particles, in addition to all the spores and pollen I'm allergic to. Bringing in filtered fresh air can take care of both problems, whether it's in a home or a car. See also user "genesis"'s signature which explains why there is a " need to clean up the OA before they bring it into the building."
    -If you won't turn it on then nothing else matters.

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