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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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    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.

  6. #6
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    I have been trying to get som assistance on high VOCs. My house has been experiencing fluctuating high VOCs that go over 3000ppb. We first thought it had to do with some leak and turned it the gas, but that was not it. We then turned off the HVAC, but that was not it. We tested for mold, but that was not it. We are clueless as to what is causing these fluctuating high VOCs everyday in the house and some suggestions as to how to identify the cause would be helpful.

  7. #7
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    Quote Originally Posted by Bnicholas1981 View Post
    I have been trying to get som assistance on high VOCs. My house has been experiencing fluctuating high VOCs that go over 3000ppb. We first thought it had to do with some leak and turned it the gas, but that was not it. We then turned off the HVAC, but that was not it. We tested for mold, but that was not it. We are clueless as to what is causing these fluctuating high VOCs everyday in the house and some suggestions as to how to identify the cause would be helpful.
    How did you determine the ppb levels?

    If this info is coming from one of the Low Cost air quality meters that have become available in the last few years - BE WARE. These devices can be VERY unreliable.

    If you want to get a accurate reading you need to perform a GC/MS lab test.
    A certified lab will send a test kit. You will provide a sample and in about a 1 week will know:
    1. Total VOC levels (TVOC)
    2. Concentratons and Types of VOCs.

    Here's two Labs I've used:
    1. https://homeaircheck.com/products/

    2. https://www.fikeanalytical.com/

    Both are OK, but Fike is better and a little more expensive.

    You can also rent a PID meter from an Environmental equipment company but will cost about $150.00/day. If you would like to explore this route - post first and I will provide some suggestions.

    Unitied States Green Building Council recommends a TVOC levels below 500ng/liters and preferable below 200ng/liter. That translates to about 200ppb - 75ppb.
    3000ppb would be about 5000 -9000 ng/liter
    Depending on the specific VOC there are about 1.5 - 3ng/liter for 1 ppb.

    I suspect your levels are much lower that you suspect. Don't trust consumer Air Quality Meters when it comes to VOCs. Also some brands are better than others.

    Curious what you report.

  8. #8
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    I have a Foobot and three Withings monitors that have similar readings. It was not like this previously and started in July. And, I have been getting sick. Also, I can physically tell when the air goes bad. I become congested. I then look at the air monitor and it just confirms what I already knew. I will take your suggestion and submit a sample to Fike or home air.

    [QUOTE=randyf;25797593]How did you determine the ppb levels?

    If this info is coming from one of the Low Cost air quality meters that have become available in the last few years - BE WARE. These devices can be VERY unreliable.

    If you want to get a accurate reading you need to perform a GC/MS lab test.
    A certified lab will send a test kit. You will provide a sample and in about a 1 week will know:
    1. Total VOC levels (TVOC)
    2. Concentratons and Types of VOCs.

    Here's two Labs I've used:

  9. #9
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    Quote Originally Posted by Bnicholas1981 View Post
    I have a Foobot and three Withings monitors that have similar readings. It was not like this previously and started in July. And, I have been getting sick. Also, I can physically tell when the air goes bad. I become congested. I then look at the air monitor and it just confirms what I already knew. I will take your suggestion and submit a sample to Fike or home air.
    I'm very interested in what you find as there are so many unknowns and a real shortage of educated guidance in these issues.
    As far as the new low cost consumer VOC meters go - the Foobot has one of the better reputation but it still suffers inconsistencies.

    There are two scientifically confirmed technologies to measure VOCs:
    1. Gas Chromatograhpy/Mass Spec (GC/MS) - this is the gold standard for determining TVOCs levels and the composition and concentration of individual VOCs
    2. PID meters - this is the only device that can immediately indicate in real time. But - Only TVOC levels can be determined and sensitivity to different VOC differs
      but it a great tool for measuring differences in real time.


    Recently a very low cost semiconductor technology to measure VOCs has been introduced. There are only 3 or 4 manufacturers that manufacturer the semiconductor chips, but lots of different manufacturers that build low cost meters based on these parts - ala Foobot, Withings and many others. I and others have used these devices and found huge inconsistencies. But there are reports of these devices improving. Many of these devices also measure Particulate pollution and I'm not convinced that there might be interference between the VOC readings and high Particulate concentrations. Have you noticed increases/decreases in Particulates readings when VOCs are high. I'd also recommend checking your relative humidity levels and noted any changes when VOC readings increase. Here's what I use to measure RH -AcuRite 01083 Indoor Thermometer & Hygrometer with Humidity Gauge & Pro Accuracy Calibration, White

    3000 ppb is huge. That's about 15x - 20x higher than the max that USGBC recommends. Here's the USGBC spec:
    :https://www.usgbc.org/credits/new-co...retail-new-c-8

    I'd recommend using Fike's services for reliability and customer service. Randal Fike is a PHD analytical chemist. He primarily services IAQ professionals but does help home owners if he thinks they are competent to perform the test.

    Note: Both Home Air Check provide two levels of testing -TVOC only and TVOC with a complete breakdown on individual VOCs.

    Before you contact either service verify that you are not seeing interference from particulates. Also when levels rise open windows and doors and see if levels come down.

    Very interested in what you find.

  10. #10
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    I have air purifies in each room and the particulate matter is usually bw 10-14ug/m. When I open a window and turn in a fan the air clears out. Last night I had the windows open pushing in air at 56% humidity for hours but I noticed that inside humidity is just 36%. The VOCs go high even with low particulate. For example, on 9/2/19 it was at 3992ppb at 4:15 pm at 49.3% humidity and 75.1F inside, particulate at 11ug/m. The outside temperature was 95%

  11. #11
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    Your a head of the game. Good data taking. I still suspect the VOC readings but GC/MS test will be the true tell.
    Very interested in what you find.

    One final suggestion: The Foobot does have the best reputation of the low cost MOS sensors, but calibration can be tricky. Have you tried to re-calibrate the device. I know that can be a hassle.

    One issue with the MOS devices is that they degrade with usage/time. Foobot, I belive, incorporated firmware algorithms to compensate.

    Could be you have an issue but less that 3000 ppb. 3000ppb is huge.

    Look forward to your next report.

  12. #12
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    I have taken it outside and recalibrated. I can try again. But yes reading in the Foobot is aligned w the reading on the Withing air mo it it in another room. It goes high very quickly, jimjnoy by 5 points every 30 seconds or so before it passes over 1000ppb. I will be doing the air test. Which test do you think is better for identifying the actual chemical causing the high VOCs. That shd help me narrow down the issue.

  13. #13
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    Quote Originally Posted by Bnicholas1981 View Post
    I have taken it outside and recalibrated. I can try again. But yes reading in the Foobot is aligned w the reading on the Withing air mo it it in another room. It goes high very quickly, jimjnoy by 5 points every 30 seconds or so before it passes over 1000ppb. I will be doing the air test. Which test do you think is better for identifying the actual chemical causing the high VOCs. That shd help me narrow down the issue.
    Here's two Labs I've used:
    1. https://homeaircheck.com/products/
    Home Air Check is an offering from Prism labs offers testing by home owners and business owners to test without using a IAQ professional. Many professional's use the same service but will tack on an extra fee for doing what you can do your self.

    2. https://www.fikeanalytical.com/
    Randal Fike is a PHD analytical chemist that was a founder and stake holder in Prism Labs. I believe he started his own company for concern of quality issues. If I had to recommend one it would Fike. Only a small percentage of his customer base are home user and you will need to give him a call to see if he will work with you. Also I'm sure he will have some input on the Foobot and related low cost devices. He's a very colorful guy that knows a lot of stuff.

    There are two levels of testing:
    1. TVOC only. This will cost around ~$200 give or take.
    2. Full VOC breakdown - This includes the TVOC test and a break down of all the individual VOCs detected. There were about 60 VOCs detected in my condo, but many were at very low concentrations. This test will run about ~400 give or take. Prism Labs might be a little cheaper but I would recommend Fike for accuracy.

    Best to keep your home buttoned up for a day or two prior to testing and, if possible, avoid cooking. Test takes about 2 hours, very easy to do, and you should have results in less than a week.

    Very curious what you find.

    Good luck

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