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Thread: Which Air Filtration is Better??

  1. #61
    Thanks Alan,

    I have recently upgraded my filters to MERV 13, and don't regret it. I also need to than Bill Pentz for all the work he originally put into cyclone design and testing...

    Ray

  2. #62
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    I am curious why everyone is happy with MERV13 or 14. Why would you not want to achieve HEPA levels? Efficiency is at greater than 99% at the smallest particles, compared to ~75%

  3. #63
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    Quote Originally Posted by Mike Nathal View Post
    I am curious why everyone is happy with MERV13 or 14. Why would you not want to achieve HEPA levels? Efficiency is at greater than 99% at the smallest particles, compared to ~75%
    First of all, HEPA is not a dust level. Dust levels are measured in particles or mass per unit volume, e.g., PM2.5 is the mass of dust in microgram per cubic meter with particle size less than 2.5 micron.. HEPA is a filter efficiency.

    An ambient air cleaner removes dust from the air at a rate determined by the product of particle concentration, airflow rate and filter efficiency. For example, if we start with a concentration of 1000 microgram per cubic meter and pass that through a fan moving 1000 CFM and then a filter with 75% efficiency we're removing 1000*1000*.75 = 750,000 microgram per minute from the air. If we change to a 100% efficient filter then we might expect to remove 1,000,000 microgram per minute. The problem is that a higher efficiency filter will usually have more resistance to airflow than a lower efficiency one. So if the fan can't push more that 750 CFM through the filter, the HEPA filter actually reduces the removal rate, making it take longer to get to a low dust level.

    Alan's excellent data clearly shows this effect. Looking at the Jet 1000B we see that the total flow is reduced from 1341 CFM to 919 CFM when the small particle filter efficiency is increased from 67% to 79%. That means it takes 25% longer to reach the same level of cleanliness with the higher efficiency filter.



    This is an example of dilution ventilation. There's not a 'clean side' and a 'dirty side' in a shop. It's all mixed together.

    "HEPA" does not mean "better", it's just a measure of filter efficiency. There's more to keeping the air clean than just that.
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    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  4. #64
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    Alan,
    check Out Filti in Lenexa KS. They will sell you the filter material used in n95 masks.

  5. #65
    I would suggest that this is not good enough. I like Winn Environmental for affordable filters.

    NOTE: Just a happy customer...

    Ray

  6. #66
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    Quote Originally Posted by Roger Feeley View Post
    Alan,
    check Out Filti in Lenexa KS. They will sell you the filter material used in n95 masks.
    They are only 1 thick filters. As per the discussion above, it might perform worse. Or maybe better. Only way to know is to test, and Im a little tired of all the tests. Plus, not cheap. But an interesting thought.

    Does anyone make HEPA / MERV 16 20x20x2 filters?
    - When God closes a door, he opens a window. Our heating bill is outrageous & six raccoons got in last night. Please God, this has to stop!
    - Outside of a dog, a book is man's best friend. Inside of a dog, it's too dark to read.

  7. #67
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    I have a friend in Reno whose family has been suffering through unbelievably awful air quality for the last few weeks due to the Dixie fire and now in addition the River fire. They've had AQIs in the 300s. In Tahoma, the AQI is 667 right now. The PM2.5 is 753.

    I gave him the directions to quickly build a few of those duct tape air filters and buy an AQI meter for the house. He's promised to send me some before and after AQI readings from the house, but I really worry about them. A few small kids, and having to breathe this stuff 24/7. He's upgraded all the house HVAC filters to MERV13, but it's a lot to ask of an air filtration system to filter out that massive amount of material.
    Last edited by Alan Lightstone; 08-18-2021 at 9:06 AM.
    - When God closes a door, he opens a window. Our heating bill is outrageous & six raccoons got in last night. Please God, this has to stop!
    - Outside of a dog, a book is man's best friend. Inside of a dog, it's too dark to read.

  8. #68
    The MERV13 filter in my furnace is indeed overwhelmed during pollen season in my area. It will be interesting to see how well they work for him. I suspect they will have good results. I also suspect they thought you "not of right mind" when you gave them the instructions.
    Thanks,
    Fred

    Seasoned professional possessing unremarkable proficiency at innumerable skills.

  9. #69
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    Quote Originally Posted by fred everett View Post
    The MERV13 filter in my furnace is indeed overwhelmed during pollen season in my area. It will be interesting to see how well they work for him. I suspect they will have good results. I also suspect they thought you "not of right mind" when you gave them the instructions.
    He would have thought I was crazy, but I gave him the link to the Ask This Old House feature about it as well as he knows my MIT / MacGyver ways since we were partners a few years ago, so he actually rushed out to follow the directions.

  10. #70
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    This is what his filter looked like after being used for one day.
    65126269418__CA82BA41-E6F6-4FBF-BE86-73C7F2FC6FDE copy.jpg

    The 20"x20"x2" filters have still not arrived for him, so this is just with 1" filters.

    OMG!!!! They are breathing this stuff 24/7, and worse outside.
    Last edited by Alan Lightstone; 08-22-2021 at 2:41 PM.
    - When God closes a door, he opens a window. Our heating bill is outrageous & six raccoons got in last night. Please God, this has to stop!
    - Outside of a dog, a book is man's best friend. Inside of a dog, it's too dark to read.

  11. #71
    Quote Originally Posted by Alan Lightstone View Post
    This is what his filter looked like after being used for one day.
    65126269418__CA82BA41-E6F6-4FBF-BE86-73C7F2FC6FDE copy.jpg

    The 20"x20"x2" filters have still not arrived for him, so this is just with 1" filters.

    OMG!!!! They are breathing this stuff 24/7, and worse outside.
    Yikes, that's how the filters look in me shop after a couple months.
    Thanks,
    Fred

    Seasoned professional possessing unremarkable proficiency at innumerable skills.

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