Page 6 of 6 FirstFirst ... 23456
Results 76 to 90 of 90

Thread: Which Air Filtration is Better??

  1. #76
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    821
    Quote Originally Posted by Malcolm McLeod View Post
    I don't know the specs on your fan, but doubt it can move enough air to actually need the total area provided by your proposed internal plenum.[/I]
    I suspect you're right about that.

    I've taken lots of data with the Lasko fan and various filters. I have no data for the multiple filter arrangement but that won't stop me from speculating! So, making an assumption about the actual fan curve I get this:
    More Filters 2.jpg
    It looks like a case of diminishing returns for more than two filters with the difference between three and four not really worth worrying about. I would just skip the top filter and make it a solid top.

    @OP, Did I read correctly, you're a RN with a wood stove in your house and don't have an AQ sensor?
    Attached Images Attached Images
    Last edited by David L Morse; 10-11-2021 at 12:49 PM. Reason: More info on chart
    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.

  2. #77
    Join Date
    Jan 2019
    Location
    Fairbanks AK
    Posts
    1,022
    When I have looked at AQ meters in the past I was looking at hanging CO/CO2 and NOx sensors off a data logger and a $3k price tag. The dylos, at a tenth of that price, is a new exciting idea to me.

    Appreciate the fan curve, even as speculation. Solid top vastly simplifies construction. Have to go.

  3. #78
    Join Date
    Jan 2010
    Location
    Tampa Bay, FL
    Posts
    2,820
    Quote Originally Posted by David L Morse View Post
    I suspect you're right about that.

    I've taken lots of data with the Lasko fan and various filters. I have no data for the multiple filter arrangement but that won't stop me from speculating! So, making an assumption about the actual fan curve I get this:
    More Filters 2.jpg
    It looks like a case of diminishing returns for more than two filters with the difference between three and four not really worth worrying about. I would just skip the top filter and make it a solid top.

    @OP, Did I read correctly, you're a RN with a wood stove in your house and don't have an AQ sensor?
    Fascinating, David. I may just get bored enough to place cardboard sheets over my fan to generate some real data, although I ultimately used a different fan than the Lasko (the NewAir WindPro 18W, which is rated at 3000cfm, but clearly doesn't do that in my experiments (my average was 955 with 4 filters on it).

    A fan upgrade from the Lasko might be a good idea too, to get more CFM. Air quality so bad as to cause visual issues with a TV?
    - 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.

  4. #79
    Join Date
    Jan 2019
    Location
    Fairbanks AK
    Posts
    1,022
    Thanks for your input and discussion folks. I built a filter box today I am calling a Poindexter box. It isn't an invention. Clearly a permutation on the TOH, Comparetto Cube and Corsi-Rosenthal Box family of filters.

    Problem: Indoor air quality
    Intervenion: Strap some good quality filtration on the box fan I am already using to circulate heat from the wood stove
    Goal: Cleanest possible indoor air
    Outcome: Cheap, effective and acessible filtration for anyone.

    Cardboard top and bottom made from the box the fan came in. 20" box fan on the front. 20x20 furnace filters left, right, and rear. Assembly time, with pictures, one hour and seven minutes. Besides the fan and the filters I used about half a roll of duct tape. Tools required: drywall knife and/or scissors. I used both.
    Attached Images Attached Images

  5. #80
    Join Date
    Jan 2019
    Location
    Fairbanks AK
    Posts
    1,022
    When I was running Corsi-Rosenthal box in the stove room next to the wood stove my convective loop to distribute heat was broken, but AQ was subjectively improved. With the Poindexter running about an hour I expect to find low speed on the Lasko is still enough air flow, even with the filtration, to keep the convective loop in operation.

    For the next model I want to move one of the filters to the bottom surface, raise the thing off the floor to let air into the filter underneath, and then have a blank panel that can be on the left or right side so the unit can be pushed up against a wall and not take up so much space in the hallway. I also want a more convenient way to seal up the fan to the filter box. This will take more than an hour to assemble, and require more tooling than just a pocket knife. I suspect the room in the hallway will be more valuable than any further improvements to air quality.

    FWIW, besides the wood stove I have a geriatric long hair cat, a house built in 1980, and I live in an EPA nonattainment area for outdoor air quality. My Dylos meter should be here Tuesday. Once I have a good idea what my indoor AQ is with the Poindexter box running I will shut it down and see how bad my indoor AQ gets while I build the second prototype.

    For folks not running a wood stove but dealing with wild fire smoke this might be an effective option if you can only find three good filters. Some online vendors sell in 3 packs, others in 4 packs.

    My thinking is by using lots of filter area and the fan on low I should capture the max possible number of fines. I can generally reload my woodstove without any visible smoke rollout, but I know perfectly well I am getting "some" particles out everytime I open the loading door. Likewise, the air exchange from outdoors when we are in an AQ alert is a relatively small amount. If I can keep this thing running 24/7, which I have been doing for years anyway, I can hopefully have a baseline low enough that peak values aren't intimidating. The cat and the house shed particles more or less continuously. If I build some 5 horsepower thing I would likely be sucking outdoor air down through the chimney of my woodstove when the loading door is open.

    FWIW I did end up with 3M filters at 2200FRP with no MERV rating on the packaging. I am a bit irritated about that as the vendor said they were MERV 13, but the 3M packaging doesn't say that. They are better filters than I can buy local, so I went ahead and put them in service.

    Will see what the Dylos says when it gets here.

  6. #81
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    821
    Quote Originally Posted by Scott Winners View Post
    FWIW I did end up with 3M filters at 2200FRP with no MERV rating on the packaging. I am a bit irritated about that as the vendor said they were MERV 13, but the 3M packaging doesn't say that. They are better filters than I can buy local, so I went ahead and put them in service.
    Those MPR2200 filters exceed MERV 13 requirements and are just short of being MERV 14.

    3M MPR.jpgMerv more.jpg
    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.

  7. #82
    Join Date
    Jan 2010
    Location
    Tampa Bay, FL
    Posts
    2,820
    Great chart, David. Thanks. That should be very useful for many people.

    So these filters really aren't efficient removing 0.5 micron particles until you get up to MERV 14 or MERV 15? They will remove some smaller particles, but will take multiple passes to remove the vast majority of them.

    Hard to be impressed with a MERV 11 filter whose minimum % of particles trapped is 20%.

    I'm having a total brain fart here. How many air exchanges are required for a set filter efficiency to remove, lets say an arbitrary 90% of all 0.5 micron or smaller particles? So as an example, with the use of a MERV 11 filter, how many air exchanges are required to remove 90 % of all 0.3-1.0 micron particles (using David's chart)?

    What's the formula to plug in the filter efficiency, and see the percent of particles removed per air exchange through the filter? Or am I looking at this wrong?
    Last edited by Alan Lightstone; 10-17-2021 at 1:19 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.

  8. #83
    Join Date
    Jan 2019
    Location
    Fairbanks AK
    Posts
    1,022
    Alan, I think MERV 11 against 0.3-1.0 micron size will get 20% (maybe a little more) on the first pass. So if your starting concentration was 100 particles per gallon, second time around the incoming air would have 80 particles in, -20%, (16 partricles), incoming air third time around would enter at 64 particles per gallon, -20% (13 partricles) and etc. I certainly defer to David, but I think that is how it works in an ideal system.

    When I run my jointer in the shop I have a fairly large pulse of particles in a relatively short amount of time. In my house the cat and whatever the house generates are relatively low volume but ongoing, people using the exterior doors are intermittent but low volume. My wood stove is a modern marvel, but I still have to open the loading door twice daily to put more wood in.

    It didn't make sense to me to build a fast, powerful filter to get the house air all clean at once given the ongoing small inputs.

  9. #84
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    821
    Quote Originally Posted by Alan Lightstone View Post
    I'm having a total brain fart here. How many air exchanges are required for a set filter efficiency to remove, lets say an arbitrary 90% of all 0.5 micron or smaller particles? So as an example, with the use of a MERV 11 filter, how many air exchanges are required to remove 90 % of all 0.3-1.0 micron particles (using David's chart)?

    What's the formula to plug in the filter efficiency, and see the percent of particles removed per air exchange through the filter? Or am I looking at this wrong?
    With a perfect filter the number of changes need to drop to 10% of initial concentration is 2.3. If the filter is not perfect then simply divide by the filter efficiency. So for a 20% efficient filter you get 11.5 exchange times.

    In general the number of change times needed to get to a particular level is the negative natural log of the ratio of desired level to initial level, divided by the filter efficiency.
    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.

  10. #85
    Join Date
    Jan 2010
    Location
    Tampa Bay, FL
    Posts
    2,820
    Quote Originally Posted by David L Morse View Post
    With a perfect filter the number of changes need to drop to 10% of initial concentration is 2.3. If the filter is not perfect then simply divide by the filter efficiency. So for a 20% efficient filter you get 11.5 exchange times.

    In general the number of change times needed to get to a particular level is the negative natural log of the ratio of desired level to initial level, divided by the filter efficiency.
    Thanks, David. My brain went on vacation forgetting the logarithmic formula for the particle decay. Man it sucks to get old.
    - 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. #86
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    821
    Quote Originally Posted by Scott Winners View Post
    Alan, I think MERV 11 against 0.3-1.0 micron size will get 20% (maybe a little more) on the first pass. So if your starting concentration was 100 particles per gallon, second time around the incoming air would have 80 particles in, -20%, (16 partricles), incoming air third time around would enter at 64 particles per gallon, -20% (13 partricles) and etc. I certainly defer to David, but I think that is how it works in an ideal system.

    When I run my jointer in the shop I have a fairly large pulse of particles in a relatively short amount of time. In my house the cat and whatever the house generates are relatively low volume but ongoing, people using the exterior doors are intermittent but low volume. My wood stove is a modern marvel, but I still have to open the loading door twice daily to put more wood in.

    It didn't make sense to me to build a fast, powerful filter to get the house air all clean at once given the ongoing small inputs.
    Yes, it's an exponential decay. With a perfect filter you would have 37% remaining after the first exchange time. With a 20% filter it would be 82%.

    You are also correct in using the average over the day of all inputs. The WHO guidelines on fine particle exposure are based on time intervals of months and years, not seconds and minutes.

    When you have an air cleaner and a source of particulates the average concentration is the average generation rate divided by the removal rate. The removal rate is flow rate times filter efficiency. So here too how fast you can clean the air also determines how clean the air is when you are continuously adding particles to it. For a 20% efficiency filter to clean to the same level as a HEPA filter you need five times the airflow.
    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.

  12. #87
    Join Date
    Jan 2010
    Location
    Tampa Bay, FL
    Posts
    2,820
    I was thinking of Scott's case where, I assume, the wood stove is running pretty continuously during many months of the year. I've never lived in Alaska (though I've visited several times, and once spent a day in Utqiagvik walking on the frozen Arctic Ocean and hoping that I could outrun the guy next to me if a polar bear approached), so I really don't know if that's true. But assuming constant generation of particles from the wood stove, I would think that the more airflow through the filters, the better, and glad to hear that Scott got good 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.

  13. #88
    Join Date
    Jan 2021
    Location
    The Woodlands, Texas
    Posts
    199
    I'm not sure I would go with a Grizzly/Shopfox air filtration unit. I expected they were all fairly the same, but I found this Wood magazine article enlightening.

    https://www.woodmagazine.com/tool-re...ration-systems

    The JET units seem like the way to go.

  14. #89
    Join Date
    Jan 2010
    Location
    Tampa Bay, FL
    Posts
    2,820
    Quote Originally Posted by derek labian View Post
    I'm not sure I would go with a Grizzly/Shopfox air filtration unit. I expected they were all fairly the same, but I found this Wood magazine article enlightening.

    https://www.woodmagazine.com/tool-re...ration-systems

    The JET units seem like the way to go.
    I have both the Jet 2000 and the Jet 1000B in the shop. The downside of the Jet 2000 is that it's quite noisy. I replaced the outer filter on the Jets with MERV 13 filters, and filtering efficiency went up, but the flow went down on the Jet 1000B, so that made it work worse, not better. It's due to the significant airflow decrease through the unit with the larger resistance of the MERV 13 vs the stock MERV 10 filter. The data is on post #63, on page 5 of this thread. https://sawmillcreek.org/showthread....s-Better/page5

    Wood Magazine's analysis was essentially the same, although I did it with two MERV 13 filters. I don't have the data here, but changing out the prefilter on the Jet 1000B to a MERV 13, but keeping the internal filter the stock one seemed to be a nice improvement in filter efficiency. And earmuffs are a must with using them on high.

    One man's opinion, but unless you have a very large shop, I personally would go with the Jet 1000B. Actually two of them, mounted opposite to each other, circulating the air in a circle.

    And if you want to improve things quite a bit, after buying the Jet, also build a cheap one with four 2" MERV 13 filters and a box fan, and put that someplace else in the shop. run both together. It really helps. I've have to do, and post another test as to the improvement in number of air exchanges/hr having the duct taped box unit added to the Jet 1000B. I've already tossed the original filters that come with it, so it would be a comparison with the Jet 1000B with a MERV 13 and then adding on an additional box filter to show how that helps.
    Last edited by Alan Lightstone; 10-19-2021 at 9:57 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.

  15. #90
    Join Date
    Oct 2006
    Location
    Manistique, Michigan
    Posts
    1,329
    I am not going to add to the technical discussion, but I have a Jet 1000B. It quit working after a couple of years. It wont stay running if it gets to speed at all. From other posts on this filter unit, I understand that there is a resistor that goes bad on the board and has to be changed. I actually bought the resister but haven't changed it. After everything I have read about filtering and particle size that affects your health, I think I will build the Pentz unit and junk the Jet. The air filter is the key, I have the Clearvue and really like it. The air cleaner uses the same type of filter - just coated on the other side so the air is pulled in from the outside to capture the dust.
    Rich Aldrich

    65 miles SE of Steve Schlumpf.

    "To a pessimist, the glass is half empty; to an optimist, the glass is half full; to an engineer, the glass is twice as big as it needs to be." Unknown author



Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •