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Thread: VOC Elimination

  1. #1
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    VOC Elimination

    I originally posted this in the residential section of HVAC-Talk. But with no response I thought this might be the right place.

    Replaced an entire attic located HVAC 5 ton flex duct system. Needed a 5 foot supply plenum for the job and the local plenum manufacturer made an interior lined one for the job the night before. Picked it up next morning and it had a very strong stink to it. We were told it was the water based latex glue curing, not to worry, it'll be gone in a day. It was installed it lit up the house with a sort of musty smell, not pleasant. After five days the smell was still there so we removed the supply plenum and replaced it with an unlined plenum that we wrapped externally.

    30 days later, the smell is still there, not as strong, but still there. Tried ClenAir odor absorbent in the return but only masked the smell. My guess is that the glue's VOCs from the original plenum has out-gassed and permeated some of the duct board distribution boxes and maybe some of the flex duct (the ducts do seen quite clean).

    We had the homeowner run the system at 90F for six hours with the windows open. Lessened the smell a bit but smell still present in supply ducts.

    We offered to install a UV Air Scrubber lamp but homeowner is worried about UV light degrading the flex duct and other components.

    We're thinking of doing a Ozone shock leaving the fan running for a few hours unoccupied. Again, homeowner is worried about ozone degrading the flex duct, rubber, etc. as well as ozone health concerns.

    Another thought was to try a fogger with Decon Five, or some sort of air cleaner system that can eliminate VOCs.

    Lousy situation to be in for all parties. So looking for suggestions, best practices. Thanks!

  2. #2
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    Dec 2015
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    Quote Originally Posted by scn101 View Post
    I originally posted this in the residential section of HVAC-Talk. But with no response I thought this might be the right place.

    Replaced an entire attic located HVAC 5 ton flex duct system. Needed a 5 foot supply plenum for the job and the local plenum manufacturer made an interior lined one for the job the night before. Picked it up next morning and it had a very strong stink to it. We were told it was the water based latex glue curing, not to worry, it'll be gone in a day. It was installed it lit up the house with a sort of musty smell, not pleasant. After five days the smell was still there so we removed the supply plenum and replaced it with an unlined plenum that we wrapped externally.

    30 days later, the smell is still there, not as strong, but still there. Tried ClenAir odor absorbent in the return but only masked the smell. My guess is that the glue's VOCs from the original plenum has out-gassed and permeated some of the duct board distribution boxes and maybe some of the flex duct (the ducts do seen quite clean).

    We had the homeowner run the system at 90F for six hours with the windows open. Lessened the smell a bit but smell still present in supply ducts.

    We offered to install a UV Air Scrubber lamp but homeowner is worried about UV light degrading the flex duct and other components.

    We're thinking of doing a Ozone shock leaving the fan running for a few hours unoccupied. Again, homeowner is worried about ozone degrading the flex duct, rubber, etc. as well as ozone health concerns.

    Another thought was to try a fogger with Decon Five, or some sort of air cleaner system that can eliminate VOCs.

    Lousy situation to be in for all parties. So looking for suggestions, best practices. Thanks!
    Yep - these can be seemingly intractable problems. See my post over the last few years.

    Here's a pdf where I summarize all the info I've collected and tried to organize for a coherent overview.
    https://www.dropbox.com/s/h01s8xnjoc...20-2..pdf?dl=0

    Here's some options:
    1. Don't give up on *back-outs* yet. There is a lot of data on success with this method.
    One of the most successful protocols is heating up inside space with windows closed for 4 - 8 hours. Then open up windows/doors and vent out for a couple of hours with the help of fans.
    Ideally this should be repeated a couple times a day for a week or more. I realize how impractical this might be, but it's been studied and is evidence based.
    See this paper:
    https://www.tandfonline.com/doi/pdf/...7.2016.1200503

    Keep in mind that VOCs boil at 120 - 400^F. So when you vent out with cooler air the VOCs will just recondense on surfaces. VOCs in the air are sourced from VOC on surfaces. This is a crucial fact that's under appreciated

    2. How well "UV PCO" systems work is an on going research project of mine. See the pdf from my results of some testing I've done. BUT - I have verified that good carbon filters can effectively trap a lot of VOCs. I've seen drops of over 60% in minutes measure with industrial metering equipment.
    Here's a link to the fan/carbon filter I referenced above:
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
    The unit is not pretty, it's loud and works great.
    But carbon has some gotchas.
    1. It will not trap all VOCs
    2. Effectiveness is reduced at higher RH levels
    3. Keep temps below 75 (or lower). Carbon can release previously trapped VOCs at higher temps.
    Good filters are also available from Austin Air and Airpura but these are more expensive and may not be as effective.

    4. UV Scrubbers, Ozone, Non Thermal Plasma, Decone 5 are based on the oxidation principle. An oxidization agent (hydroxyls, ozone, hydrogen peroxide) is used to break apart the Cabon/Hydrogen bonds of VOCs. The way the manufacturers describe it you're left with clean air plus CO2 and H2O. In the real world that's a different story. You're often left with partial breakdown products including formaldehyde. These systems can work but the data is sketchy with the kind of issue you are dealing with. The systems I've tested (I have a lot more testing to do) have not shown much effectiveness. I've talked to a lot of the providers of this gear and have found them ignorant of the data. They are usually nice guys but suckers for a story that they were told and then repeat. The data on Ozone is all over the map. It's used all the time but the data is mixed. The EPA and the scientists at Berkley Labs (https://iaqscience.lbl.gov/air-ozone) don't have much good to say, but I'm not sure they are unbiased. Of course if you do use ozone the building should be unoccupied for maybe more than a day. That smell can linger

    5. For about $150 you can test the air for the amount and type of VOCs.
    See: https://homeaircheck.com/products/

    Of course pumping in fresh air will always help.

    I'm really interested in how this works out. I've been fighting a similar issue.

  3. #3
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    Randyf, what is your opinion of ozone generators? Fire departments use them to get rid of the smell of smoke. Or at least they used to. Maybe they can be rented, I don't know. I once did a job at a company that made them and I asked what they were used for, and this is what I was told. Also hotels, to get rid of the cigarette smell if someone smokes in a non-smoking room.

  4. #4
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    Quote Originally Posted by Nuclrchiller View Post
    Randyf, what is your opinion of ozone generators? Fire departments use them to get rid of the smell of smoke. Or at least they used to. Maybe they can be rented, I don't know. I once did a job at a company that made them and I asked what they were used for, and this is what I was told. Also hotels, to get rid of the cigarette smell if someone smokes in a non-smoking room.
    Ozone treatments are probably used hundreds of times a day for just the sort of problems you mention. Most all restorations companies use them for fire/flood damage. And there are tons of companies that manufacture these devices. People that use these devices almost universally are convinced that destroy all odors. I've talk to many of them. Funny think is these folks generally know very little about VOCs. They've never heard of PID meters or Gas Chromatography (used to test for VOCs).

    Here's a great article from Berkeley Labs on research on Ozone - https://iaqscience.lbl.gov/air-ozone
    Please read - highly recommended.
    They claim, substantiated with references, that:
    1. Ozone can degrade some, but not all VOCs
    2. Some VOCs are increased. Including formaldehyde.
    3. increases ultra fine particulate matter which is especially toxic. If I used Ozone would have try to have some HEPA filters running at the same time

    Sound pretty bad but I'm not sure. Some of the studies referenced do not *seem* to use a high enough concentration of Ozone.

    Keep in mind Ozone is an oxidizer - it chops up the carbon/hydrogen bonds of VOCs. In a prefect world this would leave only CO2 and H20 - but as we all know this is not a perfect world.

    I'm open minded and curious about Ozone, despite what many PHDs (and the EPA) say. I think many of the *experts* are biased against Ozone because of the potential dangers. But the dangers are easily avoided.

    Note that Ozone is very effective against biologicals, VOCs are much harder to get rid of.








    Here's a good science article on what's really known about Ozone from the folk at

  5. #5
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    Thanks, Randyf! That is very interesting and informative.
    Did you mean to attach a second link? It appears you may have been interrupted.

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