Water and baking soda? Never heard of that one. Sprayed where? Into the ducts? What HVAC service company would do such a thing?

Can you track down where the odor is coming from? Is it actually from the heat registers? An odor is normal in the autumn when the heat first starts up for the season, but it usually dissipates in a few hours at most.

I'm wondering how the flue for the furnace was routed, and what kind of pipe was used.

I sprayed it in the air handler so it dissipated in the 3 main supply trunks.The odor is from all heat registers and it is present all the time. So to me it meant it is common to all. I thought maybe the returns are sucking in some unconditioned air so i disconnected the entire return from the furnace and i allowed the air inside the room where the furnace is to be sucked in... its a bit better but the odor still present. I looked inside the air handler cant seem to pin point the issue or find a piece of wood that would give this smell or smell anything. Hvac guys look at me like i am crazy. The flue is pvc pipe vented outside

In the summer there is less of a smell but still a damp musty smell. In the winter months I disconnected the returns from the furnace and the air inside the room where it is located was drawn in...so there was not return connected (eliminating the sawdust theory) and it still smells in all registers. The heat exchange was replaced as well as with A coil and new furnace.

sounds like DSS or dirty sock syndrome. The wood smell? what type of wood does it smell like?

The thing is DSS is a tough thing to pin point. Some times it's caused by an abundance of humidity in the shoulder seasons that allows bacteria to grow on the Evap coil (indoor coil) that bacteria produces an odor. I've never heard any one describe it as wood smell, although I think if this smell was to get confused with a wood smell if you have ever smelled cedar I think it's possible to think that.

Many people I have seen over the years don't describe the smell as anything other than stinky.

Another problem with DSS, if this is what it is -- is that in many cases the smell is due to the people living there and certain things they are doing inside the home. (Think aerosol use, perfumes, cleaners & other chemical use.)

Your HVAC system is directly tied to your homes air. If that air has something in it that feeds bacteria -- the HVAC system runs, draws air your indoor coil -- especially any recently made coil is a tight series of channels if the conditions are right for bacteria that is likely where the smell is coming from.

DSS was coined, because most often this is what it smells like.

Outside of DSS, it could be sewer gas is some how seeping into the home thru a trap that has run dry or something.

How was the condensing furnace condensate hooked up for drainage? Maybe some how some way this is contributing to the problem?

I know the smell. I can't say it smells like dirty socks tho but most people do. To me it's a VERY VERY (to the point of sickening) ozone like smell. With our heat pump, it only happens when the heat is being used and it's not all the time. Seems there are certain conditions that all have to come together at the same time. It's a mystery for sure. Ours isn't "lifestyle", it's got something to do with the coils (I think).

One thing i do want to add is if we leave our home for a week , when we comeback the house smells really bad be it either summer or winter. Sometimes we pick up the smell when entering the home after being out of it all day....and sometimes it does not smell (after being out for all afternoon)... That to me is very weird. BTW it does not help that my wife has a nose of a bloodhound.We are v clean family with lots of cooking in the house and with no pets. It is worse when there is nobody in the house for a week or more. I do not believe to be the condense drainage as I made sure there are no gasses or smell. BTW the Evaporator coil was replaced as well and once the oil burned off the smell came back.. so the DDS would affect the evaporator coil that soon.?Our smell is solid at least ...does not matter what time of the year it is....it smells lol. Is this bacteria growing some other place inside the system? So if it is DDS how do i get rid of it. would one of those air purification active filters work? or UV light on top of the evaporator coil?

Thank you for your support in this mind boggling scenario

DDS happens even if the evaporator coil and the entire furnace was replaced?? so quick ? like after 3-4 days? Now i am suspecting that if it is DDS it would be due to me spraying the famous water and baking soda in the system...which hardened into some white stuff inside the main trunk lines.( I was able to clean it off the air handler)

Most likely, the reason the odor seems stronger when you've been away for a while is that when it's in the air around you all the time, you become desensitized to it.

I don't know what you're smelling, but I don't see any reason to think that it's the baking soda.

So you had 3-4 odor free days after the furnace and evaporator were replaced? Hmmm.

DSS if this is what you have, there are many assumptions being made here. So keep this in mind.

DSS is more or less a 'bacteria' generated smell. This isn't to suggest you and your family are overly filthy or overly clean. These bacteria are small float around in the air. The conditions must be right for them to grow. They grow in cooler weather on the indoor coil, the worst smell typically comes from cooking the bacteria when you turn on the heat. Otherwise the smell produced is often a musty type smell, a type of mold if you prefer.

Primarily because of how you describe this smell coming and going leads me further to believe this is what it is. (DSS)

Treatment: removing and replacing the Evap or indoor coil is a symptom treatment. This means doing this the problem comes right back a short while later. If bacteria are in the air, running the system the bacteria find the coil again and begin doing their thing.

Another symptom treatment is to simply clean the evaporator coil. After a time, the smell returns with this option as well.

------- a possible fix ----------

This dip in chemicals fix *may* not completely resolve the issue. So realize this DSS problem is a tough problem to have.

Have a new evaporator dipped in specially formulated treatment. This is an option, but I caution you this may not work or if it does work it may only be for a short time.

Why: because companies who sell this treatment are in the business of 'selling' a treatment. The reviews they have or at least those that I can find only come from themselves. That tells me that there are most likely cases in which their product does not work as advertised. I can not find any reviews on this product from an outside source.

Note this statement: "The Dirty Sock Syndrome plagues half to 2 percent of heat pumps in the Southern states with Texas representing the lower side of the percentage. The syndrome is not brand specific, with all manufacturers acknowledging complaints. The problem itself is sporadic and limited to isolated households and is somehow related to living style or products in the home. This can be proven as manufacturers have documented changing out systems with new product and the complaint returns."

The statement above comes from this article on the subject of DSS.

For these reasons, your best bet may be to clean the evaporator coil 'professionally' and then alter your living style. (take a closer look at the various products you use in your home.)

Texas bloodhound here...if anyone in the family needs to pin down a smell, they call me. I'm a fanatic about a good smelling house. The Vent-a-Hood is always on during cooking. I even open a bag of popcorn holding at the vent so the steam can be eliminated. There is always scented/fragrant wax warming (not candles) in at least two rooms of the house. As soon as the weather cools off enough, I've got a north window open. So a good smelling and fresh house is paramount to me.

In case someone wants to point to the scented wax somehow causing the problem when it enters the guts of the HVAC, I've had DSS way before I started using Scentsy.

There is a loud "sigh" type sound the outside unit makes during a cycle (Trane heat pump). I THINK it's at that point that the DS smell CAN be released...but not all the time. It's not consistent and in my case, it's rare but it does happen a few times every winter. I can't describe it as DS tho. It's a sickeningly strong ozone smell (to me). A few nights ago it was so strong that the smell stayed in my nose and throat for hours, even burning my throat. That has never happened before. Sure wish someone had an answer.

Your house is six years old and you already replaced the furnace and A-coil (which are all metal, no wood) because you smelled wood? That's an expensive 'solution'.

Are your return air ducts a complete closed metal duct, or did they run the return air between floor joists and just cover it from the bottom with sheet metal? This would mean 3 out of 4 walls of the return air ducts are wood. Although why that would create a wood odor after 6 years is a mystery.

If you can't find the cause, have you considered an air treatment unit with an activated charcoal filter?

I guess another way of describing the smell would by stuffy. The returns run between the floor joists. I know there are air purifiers filters and UV lights that go on to of the coil..just not sure which one would benefit me the most ...a(would you recommend an Ozone generator to be ran in order to kill all bacteria?)...or it they are a solution. The A coil was replaced because it was full or the handed baking soda and when it smelled bad. After the furnace was replaced the smell came back right away, after the A coil was replaced we could no smell it because the A was oil coated so it took a few days to burn off that oil...and then the smell came back....it may have been there all along just just did not notice it due to the A coil being new. Btw before we had the A coil and furnace replaced i did have the A coil removed and professionally cleaned....and that did not work.

You say furnace, so I assume this a hot-air system. What kind of fresh air input do you have? Do you shut anything down when you leave for an extended period?

I assume you have change the filter, right? Surely.

My sister has something like this in their unit in New Orleans and it turned out to be some type of bacteria growing somewhere in the system but I don't remember the details. They had it cleaned or replaced and it has gone away. I seem to recall something about a leak of some kind.

Anyway it did appear to be something growing somewhere in the system. Their blower unit is in the attic.

Maybe it's not in the A-coil or furnace itself.

An ozone generator is for destroying odors, not killing bacteria.

I would recommend a portable air purifier with an activated carbon filter. Buy or rent one and see if it helps. If so, you can keep one or more running all the time. But that doesn't really solve the problem, only treats the symptom.

There can be many reasons. Unfortunately, the post does not transmit odor. Different odors may not always be from hvac. The smell can come from the pipes. My friends had such a case. Since they used folk remedies to eliminate the smell, they turned out to be ineffective. Cleaning the ventilation ducts helped a little, but the smell did not disappear. It is necessary to approach this comprehensively. It is better to call the wizard to determine the status of the system. The main thing is to find a company whose diagnostics are free because they can find a lot of things and without fixing the master will have to pay.

Hi, I am no expert on these things, but I was wondering if the condensate line that drains water in the summer could be drawn bad air into your system. Maybe another person that knows more could chime in.

Good Luck Woodbutcher

We had a musty smell in an attached but separate “Casita”. Our HVAC people installed an UV Unit that the say will knock down bacteria. It helped. A few weeks later, we pulled up a few loose vinyl tiles in the unit and got high quality carpet tiles. They are backed with rubber backing. Within a few days, the musty smell was completely gone. Look to your floors for root cause.

UV lights don't work. The volume of air passing through is too great. I suggest adding a GPS system to the unit, Global Plasma Solutions. We've done this to three of our homes HVAC systems. It takes care of any musty, moldy odors and mold in your house.

Also, check the humidity in your house. You may need a dehumidifier. If humidity is too high, mold can grow. It should be below 40%.

Here is another theory that needs to be eliminated. If the smell is a dirty sock smell, it can be an oil leak burning off. Is there any component of the system that uses oil or hydraulic fluid? Both smell like dirty socks and the fumes are quite dangerous to your health.

I also had an unpleasant odor in the apartment and I couldn't understand the reason for this. The ozone generator helped me get rid of this odor, but I still don't know where the odor came from.

Bumped by known necro-edit-spammer.

Depends on whether you find the mold and wash it or not. If it's growing where it's accessible, i.e. walls or floor, good, but if it's inside a wall or ceiling due to a pipe or roof leak, you may not be seeing what's causing it.