Thread: Foul odor at returns

Had a client call about a foul odor at the HVAC returns (first and second floor) when the system TURNS OFF. No odor while the system is operating. Slab home, no ductwork in floor, home was vaccant for more than a year. Client removed return covers and no signs of mold or water. Anyone have a idea what might be the cause. An HVAC contractor serviced the system prior to closing as instructed due to problems with airflow and 9 degree delta T. No odor the day of the inspection. HVAC contractor told them to have the duct system cleaned.

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Originally Posted by Richard Roshak

Had a client call about a foul odor at the HVAC returns (first and second floor) when the system TURNS OFF. No odor while the system is operating. Slab home, no ductwork in floor, home was vaccant for more than a year. Client removed return covers and no signs of mold or water. Anyone have a idea what might be the cause. An HVAC contractor serviced the system prior to closing as instructed due to problems with airflow and 9 degree delta T. No odor the day of the inspection. HVAC contractor told them to have the duct system cleaned.

You can chase odors till the end of the earth and never find them!
What type of foul odor? Does it smell like sewage? Does it smell like something died? Does it smell musty? Does it smell sower? Does it smell acrid?

Cleaning the air ducts will do little and if done wrong it can screw the air ducts up. You can only effectively clean metal ducts. Never attempt to clean flex duct, you will most likely damage the thin plastic liner.

I have not been out the home yet so I have no idea what the odor is like, however the client states the odor is making them sick and may not be able to live in the home. Just a note; the client agreed no odor was present the day of the inspection and the A/C ran for almost 3 hrs.

Check the traps on the sewer drains. There might be a floor drain on the a/c which will create an odor if dry.

Originally Posted by Richard Roshak

I have not been out the home yet so I have no idea what the odor is like, however the client states the odor is making them sick and may not be able to live in the home. Just a note; the client agreed no odor was present the day of the inspection and the A/C ran for almost 3 hrs.

If they are telling you that the odor is making them sick and that they might not be able to stay in the home, it sounds like they might have a little buyers remorse..... Document everything....

If makes little sense that you have a odor when the HVAC is off and and odor when it is running. This right here tells you that it is not associated with the ductwork or pretty much the unit. Unless it is a condensation drain like Jim noted. If it is I hope you called it out..

I would head out to the house ASAP, tonight or first thing in the morning. Take a look, show them that you are concerned. See if you can smell anything and tell them that you can or can't. Go in with the name(s) and contact information of a local IAHQ professional(s). This way you can provide them with the proper person they need to contact to see what is going on.

Condensate drains directly to the exterior, which I recommended to be relocated. I was going to the home Friday Morning and said I will like the HVAC contractor who serviced/repaired the system to be there as well, however the contractor told them to have the ducts cleaned and that is the direction they are going. If the smell is present after that, I would return to the home. At this point since everything is hidden (plumbing/ductwork) I would not know where to start to ID the problem.

Originally Posted by Richard Roshak

Condensate drains directly to the exterior, which I recommended to be relocated. I was going to the home Friday Morning and said I will like the HVAC contractor who serviced/repaired the system to be there as well, however the contractor told them to have the ducts cleaned and that is the direction they are going. If the smell is present after that, I would return to the home. At this point since everything is hidden (plumbing/ductwork) I would not know where to start to ID the problem.

Did you ask them when the odor started?

How long had they been in the home before they called you?

They are in the process of moving in. I don't understand why the HVAC contractor did not notice the odor. It is my understanding they serviced the system one and returned a second to check it and no odor noted. It has been very hot and dry up until this week when we received 3" of rain.

Am I understanding this right?

The only time they detect an odor is when there is no forced air circulation (and the windows/doors are closed)?

They smell the odor only when the air is not mechanically ventillated? Just for the first few minutes when the fan stops running, or all the time when the air is not mechanically ventillated?

There was no odor during the entire time while the system cycled for over 3 hours - before there were any personal possessions moved in?

Now that their personal possessions are being moved in, the odor shows up?

The smell is noted only at the returns not the registers or elsewhere in the home? (or does the odor spread/fill the home when the fan is not running?)

Did I get that right?

Where is the air handler? (first floor, second floor, attic)
Do any of the register vents or return vents run via the attic?

What does the odor smell like?
Do they have septic or city sewer?
Private well (and/or treatment sys) or city water?
Are they locals or new residents to the Garden State?
Near tidal waterways or brackish water?
Is there a piloted furnace sharing air handler, or a stand-alone pure A/C system (like space pak vent type)?
Fuel source for heating gas or oil? Shared exhaust vent to WH?

OK GREAT STORY

two years ago during the ugly foreclosure era. when you found every drywall with a elbow hole in it. garbage disposals removed, smoke detectors and anything else they could remove. i did an inspection. fired up the furnace. found a real bad smell coming from a bedroom heat register. i thought WHAT COULD THis BE. so i lifted the register and stuck my stupid hand down duct. what i found was at least three pounds of chopped meat loaded with magits,ants,unknown creatures and soon to be my earlier lunch. people are cruel. guess you can realize i don't do that anymore.

lost a good macaroni and cheese luch that day

cvf

Vacant homes tend to attract rodents and small marsupials who love to build nests in ductwork and units. If the ductwork is fiberduct, or acoustically lined the smell could last for ever. It may not be as evident when the unit is running due to air flow.

I was thinking more along the lines of bats. But don't know how the offensive odor is characterized yet.

The inspection cover to the blower housing should be removed and sniffed. If the foul odor is there the initial start up will blast out the odor and then the continuing airflow will dilute it out till the next time it sits for long enough to create the built up odor.

Originally Posted by CHARLIE VAN FLEET

two years ago during the ugly foreclosure era. . . . . .
cvf

Two years ago? In my neck of the woods there are three forclosures on every block and probably more that the bank has chosen to sit on.

Good story though!

And Scott Patterson's comment is very applicable: "If they are telling you that the odor is making them sick and that they might not be able to stay in the home, it sounds like they might have a little buyers remorse..... Document everything.... ". Sounds like you could be dealing with "SEWERS".