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Thread: Air Recirculating

  1. #1
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    Air Recirculating

    Hello, I am a member of a 55 member woodworking guild. It has been shut down since March 12, Massachusetts is in the process of opening the State in a 4 step process. We will be eligible for the third step. We are discussing safety issues.
    Germs in the air seem to be a huge concern. Is anyone dealing with any of these issues.
    Thanks in advance, Kevin

  2. #2
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    Mitigation via mandatory wearing of masks and keeping the number of concurrent members in the space to a limit that provides appropriate distancing is about the best way to approach this, given the high percentage of infected folks who are asymptomatic. Consider the same guidelines that any business would have to follow in your area to help develop your response and plan. While the CDC has now indicated that they believe there is less chance of transmission from surfaces, having a policy of disinfection of a machine after use, for example, wouldn't be a horrible thing. Having commercial style hand sanitizers available may also be a good idea.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
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    "Germs in the air seem to be a huge concern."
    High quantities of fresh filtered air are the best way to deal with the above. Exhaust as much air as you can replace with filtered outside air.
    NOW this comes at a cost of heating or cooling all the makeup air. Always a trade off of money versus air quality.
    Above statements are based on years of HVAC control experience in commercial buildings, University animal labs, and Hospital operating room and patient room experience including TB patient rooms
    Need information on what you have for HVAC in your building and what is available for exhaust to make any more specific recomendations.
    Good luck
    Ron



  4. #4
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    Quote Originally Posted by Ron Selzer View Post
    ...based on years of HVAC control experience in commercial buildings, University animal labs, and Hospital operating room and patient room experience including TB patient rooms...
    Are those UV sanitizing lights they sell you to put inside your heat exchanger good for anything at all and if so, do you think they can help here?

  5. #5
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    Have your meetings outside if possible. Bunch of old guys cooped up in a small shop isn’t a good idea.

  6. #6
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    This is a working shop that was accessible from 7:00 AM to 10 PM. That has all changed with this Virus. The shop is 24 x 37 with 9 foot ceilings. We are discussing HEPA filters on the Large cyclone dust collector. The room has forced hot water heat. We are also looking into some sort of air exchange system. Suggestions welcome. Any thoughts on a couple of Jet Air Filtration Units with one facing into the room and one exhausting outside? We are thinking of limiting 2 members to 2 hour shop access with time for the air to recirculate between 2 hour blocks. Mandatory masks and hand washing. Wiping down machines and hand tools doorknobs etc. We also have someone looking into UV light. This is new to everyone and we would like to do it right. Any input will be considered.
    Thanks, Kevin
    Matt you are right, we are a bunch of old guys & gals!
    Last edited by kevin nee; 05-29-2020 at 8:39 PM.

  7. #7
    Quote Originally Posted by kevin nee View Post

    Matt you are right, we are a bunch of old guys & gals!
    That describes most of us here

  8. #8
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    Kevin, that is not a particularly large room, honestly, so aside from considerations around air circulation and filtration that has largely been a part of this discussion, limiting concurrent use to only a couple or a few people is going to have to be the case. With mask use (and hand-washing/surface wiping), I don't honestly think you need the extra air circulation time. While masks are not perfect, they substantially reduce the direct expulsion of the virus from someone who is infected, so there should be less that gets into the air. That, combined with the distancing that comes with restricted concurrent occupants is a good situation.

    Mandatory temperature check before entry is also a good idea...the organization will need to acquire an appropriate device to do that measurement.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  9. #9
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    Thanks Jim, We are looking into a touch less thermometer. It wi be a couple weeks before we are allowed in. Just trying to get our ducks in a row. We would like to be as safe as possible. Also make all members feel comfortable.

  10. #10
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    Quote Originally Posted by Alan Rutherford View Post
    Are those UV sanitizing lights they sell you to put inside your heat exchanger good for anything at all and if so, do you think they can help here?
    I have only used UV lights for sanitation on a swimming pool, they worked good there
    One guy I used to work with recommended them and has them in his house

  11. #11
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    Any filter you add will not trap a virus. Your best bet for the money is removing some air from the building and replacing it with air from out side. They make some pretty efficient air to air heat exchangers that can recover heat or cooling according to the season.
    Capture.JPG
    Lee Schierer
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  12. #12
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    We've looked at UV lights in biocontainment safety hoods and in a P3 biohazard containment lab I built. To be effective they need several hours of direct exposure-- ie anything in a shadow doesn't get decontaminated, the bulbs, which are expensive, lose efficacy over a period of weeks, so need to be changed out regularly. The UV light at the right intensity to be effective also degrades many material, particularly plastics. If you rely in UV you need to have a testing program to show that your process is actually working and killing test viruses you put out in the facility. In our HIV lab we used UV inside the hoods overnight but not in the general lab space; it simply didn't work well enough.

    A wipe down with 10% bleach (or betadyne) is much more effective at a small fraction the cost. 70% ethanol is good, but takes a lot longer and more thorough exposure than bleach, plus carries a fire hazard. Maintaining containment on the source is the biggest and most critical item, trying to decontaminate is a bandaid applied after the fact that is always less effective and more expensive. In this case having a 100% mask policy (masks without rebreathers, so exhaled air is filtered) would be the most important thing to start with, that will greatly reduce the need to mitigate airborne exposure. You could also have people put on nitrile gloves before entering the facility, removing them only after exit. Combined with masks and reminders not to touch the face and eyes (I assume safety glasses are already required), you should be able to maintain a very safe facility with a 1-2x a day bleach wipedown of any touch surfaces. Of course, eating, drinking, smoking, and applying makeup is strictly verboten.

  13. #13
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    Scheduling may be a problem, especially the prime times.

    And boneheads who will not wear masks. That said, I understand some of them. Masks vary, some fit poorly, some are very uncomfortable, most cause fogging of glasses. And some people have enough trouble just breathing. Your club may want to have a series of meetings to discuss and try out various masks, not just for Corona, but for dust.

    If your recirculating DC does not have a HEPA filter already it should have.

  14. #14
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    Quote Originally Posted by Lee Schierer View Post
    Any filter you add will not trap a virus. Your best bet for the money is removing some air from the building and replacing it with air from out side. They make some pretty efficient air to air heat exchangers that can recover heat or cooling according to the season.
    Capture.JPG
    Thanks for the diagram, could you supply a brand name or suppliers? Maybe an approximate cost.
    Thanks Kevin

  15. #15
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    Quote Originally Posted by kevin nee View Post
    Thanks for the diagram, could you supply a brand name or suppliers? Maybe an approximate cost.
    Thanks Kevin
    Here is one brand, there are many others. Google is your friend for this. Since you are in Mass, maybe contact this old house team and they will feature you on their show. The Model: AE60 sells for under $500 not including tax or installation.
    Last edited by Lee Schierer; 06-01-2020 at 9:20 AM.
    Lee Schierer
    USNA '71
    Go Navy!

    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute

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