I get chemical and sewage smells from the AC vents.?

Question

The leaks were filled with foam 2 weeks ago but the smells still continue. I am worried about the kids inhaling these unhealthy fumes. Any answers on this one would be appreciated. Thanks.

Answer 1

We can probably rule out the supply ducts pulling in the odors, as the ducts are positively-pressurized and tend to push paricles away from potential leaks in the system. Let's focus in on the return air side:

Sewage odors are readily identifiable and have only one source: sewer gas. What we have to find is the connection between the negative air pressure (or suction) of your return air and your waste lines for your plumbing system. The return air supply will often consist of a chamber that the air handler sits on, with air entering through a filtered access door. Or, there may be one or more ducts from different locations in the home being fed back to a "return air riser", or a column built of fiberglass duct to direct air to the air handler.

In any event, your pvc piping that carries the waste will have vent stacks that go up and penetrate your roof. A bad joint in one of these lines, in proximity to a return air duct, would create the scenario you describe.

There is a possibility that someone piped your condensate drain into the waste system for drainage. The condensate drain is under negative pressure, and can draw fumes from the waste system directly into your air handler and distribute the offensive
aroma.

If any part of the return air chamber abuts any part of your sewer system (lines below the home, for example) the possibility for "cross-contamination" is high. The return air system must be tightly sealed to prevent intrusion from any unwanted source.

I doubt you are dealing with mold contamination, although there is one thing to consider: some molds off-gas ammonia, which is also common in sewer gas. A careful inspection of the equipment for mold and/or stagnant water might be worthwhile.

Double- check your garage for any chemicals, insecticides, gasoline, and otherwise foul-smelling items that may be drawn into the return air through small leaks. Many of my clients place their toxic materials outside in a plastic closet to insure no poison finds its way into the airstream of the home.

One client had what they thought was a serious mold problem. It was a very heavy, pungent odor with a slight chemical and biological smell. The culprit proved to be Orthene ant powder , in a can in the garage with a closed lid. Still, the fumes wrangled their way into the air stream.

Hopefully I've hit upon something here that will help. Good luck and God bless you!

Answer 2

Sounds like your drain line from the pan under the evaporator is piped directly to your sewer system. In this arrangement, there is a p-trap installed, just like under your sink except in a smaller size. If you are not getting enough condensation off your coils to keep this trap filled, sewer gasses can be pulled into the airstream. You can try to pour a cup of water on the coils (when it's not running) to try to refill the trap. If this doesn't work, try calling a HVAC repairman or a plumber to look at it.

Answer 3

I do not understand how the "leaks" in an air conditioning system would have anything to do with a sewer smell??

I would guess that the air intake (return) is close to a toilet or washer drain, and you have sewer gas coming through that. Being distributed by the ac ducts.

Answer 4

Sounds like there is either mold in the vents, a leak in the duct work, or some cirtters made a home in the vent and died.

Answer 5

check for black mold around the evaporator there is a lot of water there if there is not any mold it might be bacteria on it so clean it with bleach and water this is a common problem in the ac world

Answer 6

You need professional help. Please call an a/c heating company and tell them the problem. Lots of weird stuff can live in ductwork (i.e. Legionnaire's).

Answer 7

check and see if you have a trap on your airconditionin coil condensate drain. it has to have one