Sweet Smell from duct

[cpacpa]

There is a sweet smell coming from a few of my air ducts when I have the air conditioning running. The smell is a very sweet almost syrup like smell. Any ideas on what it is and how to get rid of it. Or should I make a service call? ANY suggestions would be appreciated. Thanks!

[teddy bear]

Mold and other biologicals generate various odors, some do not generate any odor. Keeping your ducts dry as possible limits the moisture necessary for biological growth. When the a/c operates, the %RH is high enough to grow biologicals. The a/c cycles on/off, leaving a water loaded coil in the air handler. Until the water on the coil evaporates, the ducts are wet in the off cycle. Operating the fan continuously would dryout the ducts in 30 minutes and stop mold growth in the ducts. If the odor goes away with the fan in the "on" mode, moisture and biologicals are probably involved. Unfortunatly, drying the ducts/evaporater makes your home more humid. Eliminating biological growth in duct may justify operating supplimental dehumidification to maintain <50%RH. Try the fan "on" and check the odor problem first.

[serviceman1]

This wouldn't happen to be on a chilled water system would it?

[cpacpa]

I'm not sure what you mean by "chilled water system". I do know that we have a heat pump and the entire system is a "RUDD" unit(residential). Could I be smelling Freon? What do you think?

[clipper]

Serviceman1,

Having a chilled water system would not make a difference. The dew point is still reached at the coil surfaces and condensation will form. Whether your cooling at the coil with chilled water or any variety of phase transitioning refrigerants, the end result will be the same; condensation will form on the cold coil surfaces and will have to be dealt with via the condensate drain system and re-absorption back into the air from whence it came. When the chilling stops and the coil surface temperatures come back up above the dew point, the RH in the airstream starts to rise as the water on the coil evaporates.

If the blower is running all the time, it will accelerate the drying process and will dry the coil fairly quickly. This keeps the RH in the plenum and ducts generally lower after the cooling cycle but raises the RH in the living space by some small amount after the cooling cycle as the fan flushed that humidity out of the sysetm and back into the living space. Not running the fan all the time keeps the RH in the living space a bit lower but dramatically raises it in the ducts and plenum where the moisture evaporates into a smaller volume of basically stagnant air. That’s why supply plenums, coil cabinets, and the first several feet of ductwork exiting the plenums are such prime locations for fungal growth. The moisture issues in these locations are chronic by design and when a food source is also present, the development process for fungal growth begins.

We are just assuming here that the sweet smell cpacpa reported is fungal related. I would have someone qualified take a look into the airstream portions of the system and look for the cause. It may be fungal or it may be something entirely unrelated.

[rosann]

I, too, have that sweet smell from ductwork. The smell runs throughout my entire home. Air conditioner or furnace heat, it does not matter, both enhance this smell. Please help.

[DOGBOY]

I, too, have that sweet smell from ductwork. The smell runs throughout my entire home. Air conditioner or furnace heat, it does not matter, both enhance this smell. Please help.

It could be dirty sock syndrom. Which is hard to get rid of. Try searching dirty sock and see if anything sounds (smells) familiar.

dogboy

[rosann]

dogboy.....besides the dirty sock syndrom, what do you know about a sweet smell coming out of ductwork into every room........which means this is originating in the ductwork? My furnace is fairly new, so do not think it is the furnace. However, I will check on the sock syndrom. thank you.. Rosann

[DOGBOY]

I was assuming you had a heat pump. Alot of people call their heat a furnace when in fact it is a heat pump. If it is a heat pump it could still be dirty sock syndrome as the heat pump goes into defrost anytime below 45* (a/c mode). If you have a humidifier you could still possibly have dirty sock syn. Best to have a prof. come out and check it.

dogboy

[drk]

It will not be SSS being it is a sweat smell. I have smelled insulation that can give off the smell. I'd check the insulation in the ahu for the smell

[knott]

depending on where your system is located and whats all in the same room ....sometimes vent gas can seem to smell sweet...id call your local service company

[Grasshopper67]

Vaporized antifreeze has a distinct sweet smell. i was working on several different choices and got stuck. try to google the problem.

[breathe easy]

cpacpa
Do you have an Electronic Air Cleaner or some other air cleaning device that generates ozone? Ozone has a distinct sweet smell for some people.

[mqbond007]

can 410r make a smell like sweet buring smell we have a heat pump

email back mqbond07@gmail.com

[mqbond007]

cpacpa
Do you have an Electronic Air Cleaner or some other air cleaning device that generates ozone? Ozone has a distinct sweet smell for some people.

can 410 r make your air smell if you have to much in it but they did comb out a lot of dog hair off the cioll we have a heat pump the smell is only there after we used the heat and turn on the air. They clean out the dog hair and brought my 410r down to 15 in the pink did the 410 r do it or the dog hair do it email back mqbond007@gmail.com

[La Air Man]

Have you recently replaced the ductwork? The last couple of jobs that I have done I noticed a smell when I opened up a bag of flex duct. I kept saying it smelled like syrup. It was something in the manufacturing of the duct. I know this may sound crazy but I know a few people that said the same thing.

[AirQualitySolutions]

Smells, Odors, Ductwork...

There are many causes of odors in ductwork. Modern ductwork is made from synthetic materials which can and will outgas when exposed to water. An odor may be determined to be sweet by one person and something else by another.

You may be dealing with amines. Amines are type of organic molecule which can have an odor. Tri-methyl amines are reported to smell like fish or urine. There are also Di-methyl amines.

Flexible ductwork contains fiberglass, a compound which is prepared synthetically. Ductboard is also made from fiberglass through a process similar to baking. Partially "baked" ductboard, like partially baked bread is still moist.

So, moisture and the attendant release of gases can come from production problems or exposure at the building.

Where is the duct system located within the structure and where is the structure geographically located?