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Discussion Starter #1
I have spent the last 2 years and thousands of dollars trying to resolve an odor issue in my home. The first thought is that is coming from the crawlspace. Professionals also say that you have to control the airflow. I have had the ducts cleaned and aerosesled, Attic top plates and penetrations sealed, total house weather stripped, register boots sealed, soil gas mitigation system in crawl space also attached to garage, crawlspace encapsulation and dehumidifier with Hi-Lo for the HVAC. I am still getting odor that comes through the vents when the HVAC runs. I am at my wit's end with this. Not sure what to do next. Is it possible that the odor is lodged somewhere in the HVAC unit that needs to be cleaned out? I was considering some deodorization of the wood / porous things in the crawlspace. Help!
 

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Has the AC been properly inspected and maintained?

The drain pan needs to be checked for algae and in some areas that is a big problem.

Where do you live?

Some people have UV lights installed by the AC coil to kill bacteria.
 

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I am in Georgia. Since my last post I have done a thorough HVAC cleaning. I also have a UV light. 3 rounds of mold remediation although there is no visible mold. I thought it may be a septic leak. Two septic companies say no. One suggestion having someone unclog the toe drains. They say their could be stagnant stuff behind the concrete block. Not familiar with toe drains. What does this mean? Any thoughts on this recommendation?
 

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How old is the house?
You mention a block foundation and most are hollow blocks. I have found stagnate water in blocks a couple of times. Ironically the only way it can get out is to evaporate to the inside and that path may now be blocked by the encapsulation. Was the smell present before the plastic was added?

Bud
 

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The house was built in 1984. And yes the odor.was there prior to the encapsulation. I did and redid (based on new contractor advice) the encapsulation to get rid of the odor. My current contractor does not think it is stagnant water. I asked about that because my septic plumber said the same thing kinda. He said that the toe drain could be clogged and have stagnant water or debris. I am not even sure if there are drains. But my below ground garage and crawl space both have concrete blocks so you have a good point. So do I need to open the vapor barrier and turn the dehumidifier down to 40 RH,?
 

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A dead animal in the system will surely stink the house up. But the smell usually goes away within a couple of months.
 

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Thanks for your thought. Pretty certain that is not a dead animal. Every thing has been cleaned. Plus i have working on this issue since 2014
 

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Thanks for your thought. Pretty certain that is not a dead animal. Every thing has been cleaned. Plus i have working on this issue since 2014
I can't offer any help, but welcome from Newnan.
 

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A forced air system produces difference in air pressure throughout the house forcing some air out while bringing other air in. If you turn on all exhaust fans and maybe add a window fan even though those are removing air it might also bring in the problem and the odor.

Just thinking of a way to simulate the pressure difference the house experiences when the furnace is running.

Start with just one exhaust fan and check for the problem smell.

Bud
 

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Does the odor get stronger when the heat or A/C runs.
 

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You would have to give much more information. My initial thoughts:

Describe the smell?
Stronger in some rooms, pattern with cfm supplied or distance from HVAC unit?
HVAC unit in crawlspace, where are return vents, does it have a fresh air intake?
Are air handler plenums and takeoffs taped or just the register boots at the end of the duct run?
Only when running HVAC, or when no air movement too? Whole house fan?
Crawlspace encapsulation include a concrete floor?

Some things come to mind that could cause smell but are not caused by the air handler, just moved by it:
- Mold you can't see
- High cfm pulling air out of a grease filled disposal or pipe
- Dried out plumbing trap (old floor drain, unused laundry standpipe?)
- Sulfur smell from water (open sump pit, water heater?)
- Sewage smell from downspouts or footing drain tile ("toe drain") connected to septic drain field and overcharging it
- Formaldehyde in flooring or something
- Old Chinese drywall
- Off-gassing from cheap Chinese rubber (like Harbor Freight wheel chocks)
- Cadaver buried under your crawlspace
 
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