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  1. #1
    Join Date
    Sep 2008
    Posts
    26

    Persistant unknown smell from ducts

    Have been dealing with layers of odor from HVAC system for the last 3-4 months.

    When we started up A/C in May it had a dirty maple-brown sugar smell. It eventually died down in several days, but still had nasty dank odor when A/C would kick off. We run our fan continually to filter the air so we would really notice it when the cool shut off.

    House is new construction from March of 2006. Has always had slight dusty dirty odor from vents and A/C was smelly when it kicked off, but not as bad as this year. Finally decided to fix problem and started with duct cleaning.

    Had ducts and coil cleaned about mid July on a Friday. That weekend we had terrible overpowering odor. It smelled like a muggy-dirty-stoney odor that was overpowering, especially when A/C was on and immediately following shut off.

    Duct cleaning company believed it was a defective A/C coil and came back out the following Tuesday and replaced it. Smell improved significantly. Still had an off smell from A/C however, especially when it would kick off.

    I decided to hire an environmental company who believed that the problem could be from the furnace. I mentioned to them that the furnace was run in the winter during drywall construction and was probably filthy and that we had always had a slight burning dirty smell when the heat was on. They pulled the furnace and cleaned it completely. The technician remarked that it was as dirty as 20-year-old funaces he had cleaned.

    Noticed a marked improvement for about a week, but still had an off dirty smell. Called the environmental company again who sent out a team to do a recovery level fogging of the duct system. They noticed a smell that settles in ducts when furnaces have been run with burning dust and debris on them. They also thought they smelled the sickly sweet odor of something dead coming from the return when they had the furnace opened in the basement.

    Again, marked improvement, but could now smell the odor they believed to be a dead animal that got stronger as the week progressed. The more heat and humidity the worse it would be. The day that it rained, the smell from the the vents was especially strong. It was a very heavy musty, dirty smell. We had always noticed that the odors we've had were worse with higher humidity and this smell was no exception.

    Environmental company believed we could have a dead animal in the return flex in the attic, thus the differences in smell with heat and humidity. Upon thorough investigation of the attic and the flex they could find no signs of mice, breaks in the flex, or water and mold in the attic. They inspected most of the flex with a camera also, and saw nothing. They inspected the rest of the return duct system with camera and could find nothing either, other than the company we hired to clean the ducts left more drywall dust than they should have.

    At this point, we are at a total loss as to what our problem is and where to go with it. One technician doesn't beleive it is a dead animal, but can't pinpoint what the odor is or where it's coming from. He doesn't think the remaining drywall dust that was sprayed and incapsulated should be the source either. The only recommendation at this point is an expensive HEPA filtration system. We would like to find the cause and not spend lots of money on a band aid that may not work.

    HELP!
    Last edited by gshort71; 09-08-2008 at 05:12 PM.

  2. #2
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Does the system have a fresh air intake drawing air from outside?
    If more government is the answer, then it's a really stupid question.

  3. #3
    Join Date
    Sep 2008
    Posts
    26
    One return in upstairs hallway and one return on main floor. No fresh air intake.

  4. #4
    Join Date
    Mar 2005
    Posts
    997
    Id call the duct cleaning company back and have them clean the duct again! They should have cleaned the duct and the AHU the first time. Maybe you can get some money back since they did not clean the AHU.

  5. #5
    Join Date
    Sep 2008
    Posts
    26
    I am having environmental company come out and clean both air returns completely. It appears we are getting the odor from the dry wall dust remaining in them. It was never this intense or pervasive of a smell the first two years we lived in the house, however. It seems to have gotten so much worse from the partial cleaning we got in July, which left a thick coating in one return and small piles in the other. Very humid or rainy days make it almost unbearable to breathe. Can drywall dust in returns along with elevated humidity cause this?

  6. #6
    Join Date
    Dec 2007
    Location
    Cedar Grove, Wi-Sheboygan
    Posts
    1,582
    You do not make any mention of crawl space's or water seepage in your basement which could potienally be the problem. If you have a musty wet basement and have a air return in your basement which since you are running your fan 24/7 will pull that odr or musty smell from your basement and crawl space. Believe it or not I just came from my parents home and when I walked in they had a very strong musty odor which was coming from there basement because it is alittle damp but they had a small cold air return which was sucking in the odor from there basement and spreading it thru out there home, so I closed it off and turn the fan on high for about a hour and opened a few doors and windows and the smell was soon gone. Do you have a cold air return in your basement ? If you do close it off and see what happens after a hour or so with the fan on high and fresh air allowed to circulate thru out the home and see it that helps with the odor your claiming your home has.

  7. #7
    Join Date
    Sep 2008
    Location
    Lafayette, IN
    Posts
    95
    I'd suggest looking into a UV-light. These lights are very powerful ultra violet radiation lights that kill dust mites bacteria and mold. They're usually put above the a-coil to deter bacteria on the coil but they kill everything air born as well.

    I used to do duct cleanings. Sometimes you'll just get a thin residue of drywall dust, spilled drinks, food, normal dust, rotted mice, spider webs, etc... that can't be cleaned. The fogging should have contained it but, it sounds like it might just be residual bacteria that the fogging didn't contain for whatever reason.

    Whatever the case, UV lights would definitely cut down on the smell and prevent further problems in your coil.

    These are not an inexpensive fix but will improve the air quality in your home. (cheaper than a hepa and better on your blower motor, heat exchanger, etc etc etc...)
    Build a man a fire and you keep him warm for a day.
    Teach a man it's ok to stand in a fire and you keep him warm for the rest of his life.


    - "If you were able to chose the kind of brain injury you were to incur, it would be better in terms of the potential for recovery to have a stroke, concussion in a motor vehicle accident, etc. than carbon monoxide poisoning" -- coheadquarters.com

  8. #8
    Join Date
    Sep 2008
    Posts
    26
    Actually, our basement is dry with no musty odor and it does'nt have a return. We have had UV lights above the coil for several years. We just changed the bulbs in May, so they are fresh and working.
    The environmental company did a manual wipe down of the main floor return and supply today. The technician had been working with ducts for years, from cleaning new home ducts to special recovery services such as fire damage. He said he had never seen such a heavy coating of drywall dust. Evidently, all the dust from the drywallers sanding wound up caked in the duct work. Air whips were unable to get it. When the dust met with the damp cloth, I could smell what we have been experiencing.
    It appears this was it. He is coming back to finish up tomorrow. It already seems improved. The only thing I notice is that for about 8 minutes after the A/C kicks off and the system is blowing out the remaining humidity, I'm still getting a rather strong odor in both the upstairs and downstairs vents. The upstairs supply trunk wasn't cleaned so I'm not sure what is still going on. The odor is almost a sickly sweet smell that fades away gradually.

  9. #9
    Join Date
    Sep 2008
    Location
    Lafayette, IN
    Posts
    95
    Builders are so careless about drywall dust. Worst thing ever for a system and it comes standard with every home.
    Build a man a fire and you keep him warm for a day.
    Teach a man it's ok to stand in a fire and you keep him warm for the rest of his life.


    - "If you were able to chose the kind of brain injury you were to incur, it would be better in terms of the potential for recovery to have a stroke, concussion in a motor vehicle accident, etc. than carbon monoxide poisoning" -- coheadquarters.com

  10. #10
    Join Date
    Dec 2007
    Location
    Cedar Grove, Wi-Sheboygan
    Posts
    1,582
    When I have friends that are building a home for the first time I tell them to cover all there duct work from the first day it is installed and do not let anyone turn on "your" Furnace, if they need heat tell them to bring in there own !!! That dust is so fine and heavy and it gets worse when it meets up with humidity and you end up with the probelm you encounter with caked on drywall dust thru out the entir system.

  11. #11
    Join Date
    Aug 2008
    Posts
    6
    Quote Originally Posted by gshort71 View Post
    The only thing I notice is that for about 8 minutes after the A/C kicks off and the system is blowing out the remaining humidity, I'm still getting a rather strong odor in both the upstairs and downstairs vents. The upstairs supply trunk wasn't cleaned so I'm not sure what is still going on. The odor is almost a sickly sweet smell that fades away gradually.
    We have the same problem. However, we'd been living here (new construction) for a while. It didn't do this at the beginning.

    We have the A/C on during the day or the windows open if its cool enough. We turn the heater on at night during fall or winter, when cold enough at night. It reeks of must or mold. The smell mostly goes away after a while. We're not immediately going from a/c to heat. We make sure there's a downtime between the two. It seems worse when we've had the unit off and the doors or windows open.

    We had the installer out to check and fix it. The replaced the coil and plenums but this didn't help.

    Their final word was a UV lamp. I don't get this since it wasn't always a problem.

  12. #12
    Join Date
    Sep 2008
    Posts
    26
    Problem has been isolated.

    After months of dealing the odors and cleaning everything possible, we still had substantial odor which I managed to track down to the only location left, the wall return. The company I'm working with gave me two options, spray paint down in there or take out drywall and line it with metal ductwork. I chose to line it. They cut out the drywall and believe it or not, I got the smell. It appears the wood is still potently strong after almost 3 years out from the build. I never thought wood could smell for that long or the way this does. The smell changing with humidity now makes since due to the wood absorbing the moisture.

    Note to future home builders. Get your wall returns lined with ductwork during the build.

  13. #13

    Problem solved?

    Hi there,
    I'm wondering if you had this problem solved? I'm experiencing something that I think is very similar and wondering how you resolved this. Did you have any health complaints?


    Thanks ,
    L

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