21 answers

TERRIBLE, Terrible Smell!!

Hello moms!!
Since 3 ½ yrs (!) we’ve been experiencing a terrible putrid and sewage like smell that comes into the house when we turn the furnace on! Now that I am pregnant, you can only imagine how my sense of smell has been suffering!!!
Here is the caveat: *not always* when the heater is on, will the smell rise!! The other interesting fact is that when we first moved into the house, there was no bad smell problem whatsoever! It started to surface a few years later. We tried everything from cleaning our ducts, checked the heater system, had a pest control guy come out to see if an animal had died in our basement, we smoked out the house to see if we had any leaks in any of the pipes leading into or out of the house and we called the sanitation district for help. NO ONE can figure out why the smell is entering our house and what is the cause of it!! We are sooo desperate and are hoping that someone out there has had a similar experience and can help us find the solution. Winter has become unbearable for us as turning the furnace can turn the house into a sewer pool! The only thing to be thankful is that we live in Northern California and not Minnesota! We appreciate any advice!!

2 moms found this helpful

What can I do next?

So What Happened?™

Thank you to all the wonderful moms out there that did take the time to answer my question! One of you mom's even offered their husband's expertise (which I did take - gladly!). All the signs are showing towards some plumbing issues and threfore that will be our next step! I am soo thankful to have found this support group!
Happy Holidays and a prosperous 2010!!

Thousand thanks again!

Featured Answers


I had a similar problem and it too became a more distinctive smell when I was pregnant. It was like an old musty smell, well it happened to be mold. It was in the walls of the are I was smelling. We had a GC come in tear the wall down make the proper repairs to the wall and now the smell is gone. Somehow there was some water damages from a long time ago and eventually it started to get worse. It should be taken care of as soon as possblie, don't want to have anyone breathing that bad mold/mildew. Anyhow, good luck!

Maybe a mouse or a rodant has died in the system. We have horrible problem with mice where i live. Call the county and ask what they can do to help first. Good luck.

More Answers

Dear M.,
Sorry you are going through this.
I have to say I got a kick out of you saying you live in Northern California. We live near the Oregon border. To me, THAT is Northern California. We can freeze even in the summer.
That aside, when we first moved into this house, we noticed a horrible odor and then next thing you knew, we had sewage pouring out a vent on the side of our house. The landlord refused to do anything about it and said my son must have broken a pipe with his bicycle. (?????)
Anyway, I called the city and they came out. One of their underground pipes had burst. To make it even worse, if someone up the street turned on their shower, washing machine, dishwasher or flushed their toilet, it started spewing out in my yard and at the sidewalk where the meter is. It was HORRIBLE!!! That smell came up in the bathrooms too although the toilets or tubs never backed up in my house. They had to dig the entire street up to fix it. They got mine fixed and then it all backed up in my neighbor's basement instead. The city came out and sucked all that horror up, bleached and disinfected her basement and had to dig the street up again. It was a real mess, but the City took care of it and we were never charged a single penny because it wasn't our fault. My landlord tried sticking me with the huge Roto Rooter bill and the City paid that too.
I'm just saying...have public works check everything thoroughly. It could be a dead animal, but one animal shouldn't smell that long.
I do hope you get it figured out. You need to be able to use your heat. Being pregnant and smelling that can't be good.

I wish you the best!!!!

1 mom found this helpful

I'm a restaurant facilities manager, and so I have seen many dozens of similar problems. A foul smell like this is almost always related to the plumbing system. (I am guessing that you don't continuously have animals dying under your house - seems like you've already checked that.) If you've not already checked these areas, here's what I'd suspect:

1) Find the fresh air intake on your heating system. Now, is there a floor drain nearby? If so, pour water into it (about a gallon should do). Sometimes the p-trap in a floor drain will dry out, and so sewer gas is able to escape into the air that you breathe. It smells terrible, but fortunately it's a very easy fix!
2) If there is no floor drain, is there a hand sink, laundry sink, mop sink nearby? Check to be sure there has been water poured down those drains recently too.
3) If none of the above applies, is there a toilet nearby? Replacing the wax ring under the toilet may solve your issue (or sometimes 2 wax rings are needed, but only 1 has been installed - again, an avenue for sewer gas). If not, see if there is a plumbing vent pipe running through the wall. If so, it may have a crack in it - this would also allow sewer gas into the air.
4) Last resort, have the sewer lines in the area video'ed by a plumber. There may be a crack or hole in one of the sewer pipes. This is actually fairly common in homes of a certain age (and/or if bleach or drain-o has been used a lot). If there is a hole in one of your sewer pipes, I would check out a Trenchless plumbing company - yes, it's a bit more expensive up front, but you will have NO damage to the floors/walls in your home, so in the long run it's cheaper. I have used trenchless plumbing repair many times with great success.
5) If nothing above works, then you may have mold/mildew growing inside one of the adjacent walls. If this is the case, you'd be able to see it - the walls would feel squishy and would smell awful. I promise this is not as scary and expensive as you probably imagine. All you need is a good GC with experience in this area - they can safely remove any affected drywall, fix whatever's leaking inside the wall, and close everything back up. (We do this ALL the time in restaurants - typically for us it's an overnight job.)

I hope these suggestions help. If you need any contractor recommendations, let me know! I have managed maintenance and construction all over the state so I have a pretty big list of good contractors if you need it.

1 mom found this helpful


I had a similar problem and it too became a more distinctive smell when I was pregnant. It was like an old musty smell, well it happened to be mold. It was in the walls of the are I was smelling. We had a GC come in tear the wall down make the proper repairs to the wall and now the smell is gone. Somehow there was some water damages from a long time ago and eventually it started to get worse. It should be taken care of as soon as possblie, don't want to have anyone breathing that bad mold/mildew. Anyhow, good luck!

we also had some foul sewage type of smell coming from our basement a few years ago, we thought we did not have enough ventilation. Turned out that there was a leak at the drainpipe underneath our kitchen sink and a lot of food stuffs had leaked out onto the basement floor and got rotted and smelled (the smell came out from the garage/laundry area and entered the house). We had a plumber to come and fix the leak and clean out the rotted food and the smell was gone.
Good luck to you!

My husband says that some furnaces have something underneath, a sort of cavity that goes down under the floor. He forgot what it is called, but he said that maybe there could be a pipe leak under the house, and some of the leaked matter could get under there and the furnace might bring out the smell.

We had a smell for about two years, that would happen occasionally. Sometimes it smelled like something died, other times more like mold. WE recently learned that we had a leaking pipe under our kitchen area, so I guess the sink disposal stuff was leaking under there all that time.
Anyway,the plumber said he can sometimes tell about those kinds of leaks because these tiny flies usually hang around the house. (We had seen some.)
Try talking to a plumber. He may have ideas, or he can just crawl under the house in the area of the furnace, and see if it is wet under there.

Do you live near a rendering plant/downwind? I'm thinking some smell is getting sucked in during heat exchange.

Are there a lot of deciduous trees around (I'm thinking rotting leaves in raingutters or standing water near the vents)

Also, some molds give off bad odors when warmed up.

However, the most likely cause is something dead inside the vents, but I feel like it would have gone away by now if you've been there a few months. Once something is decayed enough, it no longer smells intensely.

Other things: Could it be offgassing of furniture? Could it be termites (they smell very distinctly like old urine to me.)

Have you tried burning candles to counter the smell? If it's not methane, it's not going to blow up, and may give you something pleasant to breathe while you're trying to get through this time. I'd also suck on peppermint lifesavers if you can, or dab a little mentholatum under your nose since that will block smells too (temporarily).

Are you sure nothing's dead in or around the furnace? Also, we have a sewer manhole in our yard and it smelled so I called our county and they re-sealed it. No more smell. Ours had nothing to do withthe furnace though....that's a strange one. Good luck.

Maybe a mouse or a rodant has died in the system. We have horrible problem with mice where i live. Call the county and ask what they can do to help first. Good luck.

Are you buying or renting the house? I'd contact my homeowners insurance and explain the problem and see if they can send a few more agencies out to check ducts or dead carcasses under the house somewhere. If you are a renter you should get a few of your visitors that notice the aroma to write out affidavits and submit them to your Landlord with a request that he/she investigate further. Tell him/her that you wont pay rent until they figure it out. Let us know when you solve it.

Megan B and I seem to have shared this problem. We live near a field and rats find the smallest holes and get into the house. This rat died between the walls and is smelling up the house something terrible, too. We have had this problem in the past and can't get the rat out so we have to live with the rotting smell. Even worse when the flies come, gag! We have several strong burning candles to help cover the odor, but it's a waiting game. Hopefully, you can find a strong candle that doesn't bother you and a good spray of febreeze. Good Luck!

We had something similar with our hot water heater. When the heater furnace was ignited, this foul egg smelling odor would permiate through the hot water. It had something to do with the propane and some certain component in the water heater. We changed put the water heater and the smell has been gone ever since. It was something about the coating or materials used in this certain hot water heater and when it came in contact with the propane. Not sure if any of this helps with your situation. Good luck to you!

Hi M., that must be miserable esp. with morning sickness!
Thankgoodness it's not our house but in the garage & the smell was dead rats from the near by field. We got several cats andthey live in the garage now so that fixed that problem-- but we sure had to toss a lot of things out because of it.
I watched a show on TV about animals that either nest or go to die in people's vents-- since then we have had ours checked. So you might consider that. We had a pest control company come but theremay be another way to do it. Good Luck and Happy Holidays, Nana Glenda

Maybe an animal is pooping under there periodically? Maybe your out going water pipes have a leak?

When you do smell it inside - can you go outside and smell it anywhere out there?

Good luck!

Does your house have a crawl space below it? There could be something down there, or burried under there. Also there may be a dead animal in a wall in the house. My Aunt and Uncles house has a drainage problem and they keep having to dig out where the sewer meets the house. It keeps leeching into the ground instead. Just some suggestions. Good luck
W. M.

Call Youngs Heating & Air Conditioning and talk to them. They have been in business forever and is the best company out there. Maybe they will have some thoughts. O, they are quite reasonable too. But I am thinking since they are a family-owned business for years and years and years, that maybe they have encountered a similar problem over time and can help you.

Hi M.,
I was just talking to my husband about your problem. It sounds like you have tried a lot of things, but he was suggesting you call one of the Restoration companies that clean up after fire or flood damage. They have very powerful machines that clean with Ozone. I witnessed the power of ozone once in a smoke saturated hotel room. A friend brought their ozone machine in and let it run for about 30 minutes. We couldn't believe the difference. Even the bedding had no smoke odor.

You probably need the commercial ozone machine to be placed in your home with the heater on so it has access to all the pipes. You wouldn't be able to be in your home for the treatment. The added benefits is that it kills dust mites and all the odors in your home. My husband thinks it might only take 3-4 hours. Does your heater have an option for using just a fan, or is it heat only?

Has your home been tested for Radon? Do you have something that monitors carbon monoxide? It could be leaking past the heat exchanger in the furnace. Another thing, Art wondered if a rat had gotten into the heater exchanger. It would cause a horrible smell. If the blower comes on without the heat do you still have the smell?
We hope this will help.
D. and Art

There was some problem with drywall manufactured in China a while back. I think one of the chemicals used would give off a bad odor and the drywall would start falling apart. Here is a link to a NY Times article:


Do you have a sewer system or cess-pool(sp)?? If cess-pool, maybe it is somehow leaking, but don't see how the furnace would affect it. All I can think of- Good luck.

My suggestion is to get room heaters for the bedrooms until you find out what it is that is causing the smell.

I still have Racoons (past 2 years) in my attic and can't figure out how to get rid of them. They have had babies, so I have several. Have caught a few in a cage and take them to a farmer who takes them up to the mountains. I think they invite others from down the street because my attic is so large ;>). I live in the city of Sacramento, all of their habitat is gone with construction of malls and homes, so the little guys have no where else to go.

Oh dear. Okay the only thing I can think of is a dead rat that has crawled under the house, attic or between the walls, it doesn't necessarily need to be in the ducts, (this has happened to us: rat crawled into wall and under house after eating rat poison. sad but stinky.). Also, call the city and see if your house is built over any kind of sewage/landfill. And do you have a septic tank? If so, you need to have it sucked out/dumped once in awhile. Hope that helps. Good luck!

Yes, we had this happen.
First, a skunk would visit at simialar times every few days (hide under the house when it got cold). The smell was both inside and out.
Another time it was sewer, only inside the house and no real why when it happened ( smell was worse when warmer)It was the snaking of the drain created a hole that opened up/ blocked up at times, in the wall behind the bathroom sink.
During construction the entire pipe was exposed, It was so bad that the whole wall needed to be torn-out and sewer down to the main replaced.
FYI_ When tree roots broke the main sewer line the insurance did cover that, years ago)

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