Help Me Figure Out This Mystery House Smell

March 31, 2024 10:33 PM

There has been an odor in our house that comes and goes, for nearly the last ten years now. My husband can't smell it, but it's sometimes so intrusive it keeps me up at night. Description inside.

So, I know what dead animals smell like. We have a gas stove and I know what a natural gas leak smells like. I know what dry rot smells like. This smell is not those things. It's something that I always describe as "basement smell", but our basement doesn't smell as bad as this (our basement just smells like an ordinary basement, the crawlspace even less like anything). It's a musty but not earthy smell, with a salty tang like old meat. No rotten egg or sulfuric odor. Sometimes it leans toward a gas smell. I don't know how else to describe it. It's not always around. Sometimes it shows up for a few days, and sometimes disappears for weeks. The smell happens any time of year, most often in the evening and through the night though often disappears in the morning. For some reason I associate it most with rainy days, but is not exclusive to rainy days. My husband can't smell it, but he is not very sensitive to smells.

I used to think it appeared when our drafty 1914 bungalow had the heat on, and cooler air was bring sucked up from the basement/crawlspace through the floorboards. Now I'm not sure because that's not always consistent. I smell it in the front room and both the bedrooms. It's not coming up through the furnace vents.

We discovered we had a cracked furnace exhaust pipe in the basement and had it repaired, but that had no effect on the smell. We do have a couple basement drains, and a basement sump with a pump that was here when we moved in, but we've never used it. I don't smell this smell near those drains, or anywhere in the basement. I just walked around the house and I don't smell it anywhere outside even though I am smelling it in the living room. I don't think I've ever smelled it in the bathroom or kitchen.

Possibly relevant info: we have an attic accessible by a hole in the ceiling. We have natural gas from the city, and city sewer. Our stove, dryer, water heater and furnace are natural gas (I just sniffed around the furnace and water heater and don't smell the smell). We have a air purifier that is triggered by particulates in the air, but this smell does not seem to trigger it.

I'm at a loss for figuring out this stink. I'm hoping someone has some other ideas of where to investigate or what it might be, even if they seem far-fetched.

posted by oneirodynia to Home & Garden (31 answers total)

Try cleaning your refrigerator drip pan. That was the gross mystery smell that plagued my house once for months before I realized there was such a thing as a refrigerator drip pan.
posted by qxntpqbbbqxl at 11:00 PM on March 31 [7 favorites]

This doesn’t sound quite like what you’re describing, but it’s worth knowing that electrical faults can give off a fishy or ammonia-like smell.
posted by ceramicspaniel at 11:21 PM on March 31 [3 favorites]

It’s probably water related. Something wet produces the smell, has the smell most of the time, but only releases it sometimes.

So anything in the house that uses or produces water is suspect. Like the washer or dishwasher drain can have stank water in it, and not used for a time, could evaporate to a point the smell from them starts to escape. Make notes of that stuff every time you smell.

But, the idea you sort of associate it with rain makes me maybe think of cracks/ leaks in a plumbing vent line. Changes in outside atmospheric air pressure due to weather (increases) slightly limiting the natural venting and causing those smells to seep from the crack/leak.
posted by ixipkcams at 11:33 PM on March 31 [2 favorites]

For me what you're describing sounds like the smell high rise hotel rooms have, when they don't have enough natural ventilation (real opening windows), and the 'used air' smell kind of saturates into everything.

You also mentioned it can be worse on rainy days, which could be when you're less likely to have windows open and a good through flow of air to clear through the lingering smell trapped in the pores of your walls and furniture.

But yeah, as others have mentioned above, the smell could be coming from so many places. And when you're really sensitive to smells it can be infruating trying to track it down.
I wish you good luck in finding the source!
posted by many-things at 12:37 AM on April 1

What kind of traps do your sinks have? If they are old, the gas may come up the pipe. O paid the plumber to change mine. Another time, the smell was my furnace burning where it shouldn’t!
posted by shockpoppet at 12:37 AM on April 1 [2 favorites]

Are stinkbugs a thing where you live?
posted by minervous at 12:41 AM on April 1 [1 favorite]

Mildew?

I had a mystery smell in my last apartment, localized near the kitchen drain, and I went crazy trying to clean it and then called the super - and he said it was probably mildew coming from the cabinet UNDER the sink. Some Damp-Rid under the sink would take care of it, he said - this is a desiccant dehumidifier thing, where it's just a coarse powder that soaks the humidity up out of the air. Periodically you just have to pour out the accumulated water and refill the tub with more powder. I got that and it worked perfectly and I never smelled it again.

It's cheap and you can get it at lots of hardware stores and at places like Target.
posted by EmpressCallipygos at 4:39 AM on April 1

I'm gonna bring it up just because....has anyone smelled it besides you?
I'm a cis female migraineur so I'm really good at, for example, smelling out actual gas leaks and mildew, but also imaginary smells.
I hope you take it with no disrespect for your experience, but the smell of strawberry jam in my bathroom was probably not real. (Also, smelling toast is NOT a sign of a stroke!)
posted by atomicstone at 5:49 AM on April 1 [3 favorites]

Not sure what you mean by basement smell but it makes me think of church/castle smell? If so, could be mould.
posted by run"monty at 6:13 AM on April 1

Plumbing vent line issues or mildew/mold were my two guesses, already suggested above.
posted by Dip Flash at 6:35 AM on April 1

It's worth double checking your fridge's veggie crispers for anything fuzzy.
posted by brachiopod at 6:40 AM on April 1

First thing I thought of was that there might be a perforation somewhere in your sewer line. You can have it scoped by a professional, who will use a tiny camera on the end of a long, flexible rod, for a semi-reasonable fee.
posted by Dr. Wu at 7:39 AM on April 1 [1 favorite]

Second vote for "sewer gas" aka a hole or perforation in the sewer or waste water/drain pipes in your house.

For an astoundingly well written description of this problem in an old house please check out this Harper's Magazine piece by Jerimiah Sullivan.

Wow what a contrast between the brotherhood of workers sharing a trade, and man's inhumanity to man, right?(and yes, they are all Men in that article.)

I have experienced this twice. Once in a 100 year old commercial building in a city with combined sewer and storm drains. The roof drains went into the sewers, and when it rained the water level rose in the sewer pipes below the building. That water pushed the air in the sewer pipes (and all the watery, musty, stinky smells) up, and that air has to go somewhere. A hole in a rusted cast iron pipe the size of a penny made enough bad stink to shut down the room for half a day. I fixed it with duct tape - not water tight but it just needed to make the bad air keep traveling.

I also had this in my own house, that had a failing Air Admittance Valve on the wastewater drain pipe from the washing machine. Lucky for me, the city was doing a smoke test of the main sewer pipe in my neighborhood, and I was working from home, so I saw the wisps of smoke coming out the air admittance valve. Replacing that valve solved it.
posted by sol at 8:21 AM on April 1 [13 favorites]

Do you have any female friends who could come over and sniff around with you? Women tend to have a better sense of smell than men, which is likely why your husband doesn't notice your mystery odour. Other things I'd look into: trees around your property with a foul odour (linden and acacia trees, for example), mice or other pests, your floorboards, baseboards, etc. I lived in a place with stinky woodwork and it got worse whenever it was humid.

Don't let anyone convince you that you're imagining it. If you were, you'd smell it everywhere, not just those three rooms of your house.
posted by Stoof at 9:06 AM on April 1 [2 favorites]

Any chance it is dust burning? How recently have your filters been replaced and/or have you ever had your ducts cleaned?
posted by capricorn at 10:12 AM on April 1

1) Maybe it's flooring related? You've never noticed this odor in the kitchen or bathroom, where floors are usually tile, linoleum, or vinyl. Could be mold or mildew under an area rug, or in a disintegrating pad under carpeting. Or, an area of damp wool re-activated by rainy weather. Check for radiator drips, window seepage, clammy rug patches in the rooms with the smell (and the offending area might be under a piece of furniture, or behind it).

2) If your home has a chimney, or *had* a chimney that was closed up during hvac modernization, that could be a source of intermittent 'musty' odors.
posted by Iris Gambol at 10:46 AM on April 1

Others have mentioned the sewer gas option. Or could it be some kind of anaerobic mud/swamp situation? Do you have water or drain pipes running under your living room? When we had a weird smell, it turned out to be a cracked drain pipe leaking water into the yard. It could be worse during the rainy season as it would dry more slowly if the surrounding area is wet or even if ambient humidity is higher. If it was a supply line leak, you could test for it by turning off all faucets and looking at your water meter, but that wouldn't help with the drain pipes. Is it gone when you come back from a vacation and worse when you're doing a lot of showering or dish washing?

The other thing is that a cat once peed on our floor, and it soaked in in a way that it took about five years for me not to smell it when the room had been closed up for too long.
posted by Spokane at 10:51 AM on April 1

Where in the house does it seem to be concentrated (if anywhere)? Could it be a dry trap underneath a washing machine?

Has anyone else ever smelled it? I had a phantom smell for years that was SO powerful and which I still haven't figured out the cause of.
posted by saladin at 11:02 AM on April 1

Response by poster: Thanks for all the ideas! A few clarifications: I've been smelling this smell for years, so it's definitely not something in the fridge :-) . Unlikely to be the fridge drain pan either- we've had a new fridge in the last year. No obvious or un-obvious wet in any of the rooms I smell it in. In the Bay Area, our house dries out pretty thoroughly over the 5 months of no rain.

Has anyone else ever smelled it?

If they have, they are too polite to say so ;-). As far as I can remember no one else has been here when the smell has been noticeable to me. I definitely would have asked them about it.

We have wood floors and move or change the area rugs regularly. We occasionally see a stinkbug in the yard, but not in the house. We recently (like in the last 5 years) had all our ducts replaced so they should be relatively free of dust. It's not a mold or mildew smell- I should have said that I know what those smell like too. It's not really an obvious sewer smell (I've lived with a not great septic system before, that always had a smell around the cleanout and tank caps), but the sewer gas and sewer vent ideas are great suggestions for us to check out. I was telling my husband last night about my idea that there might be a crack in a sewer vent somewhere in our attic and maybe that's what causes the smell. It doesn't explain why I don't really smell it in the bathroom or kitchen, but at least it's something to look into. WRT pipes under the rooms, all the sewer lines exit to the right of the house before the front room, which is where I most often smell this smell. The water line from the city does enter the house below the front room, but there are no water lines (or pipes of any kind) below one of the bedrooms where the smell appears.

Is it gone when you come back from a vacation and worse when you're doing a lot of showering or dish washing?

It's not been here when we've returned from vacation that I remember, though our house does have that old house dry rot smell and that's very obvious. Generally our house is very drafty, and we frequently have windows and skylights open because I am a fresh-and-moving-air fiend. I have never noticed a correlation between using lots of water and the smell.

Iris Gambol, our house does have a closed up chimney. I suppose that could be stinking up the attic somehow... hmmm. Seems like I should try and smell the chimney and get up in the attic and poke around.

And sol, that Harper's article was excellent. Thanks for posting that. I will investigate our air admittance valve.

Something I didn't mention before because it just seems too wacky and may confuse the issue, is that when I am in the main bedroom while the smell is happening, in that room it comes along with a strong laundry detergent smell- but not the laundry detergent we use ( I am sensitive to laundry perfumes so we don't use anything with much of a scent). I feel like this makes me/the situation sound even more fantastical. I can usually tell when our neighbors on either side are doing laundry, but I get the laundry smell in the middle of the night along with the weird salt/meat/basement smell.
posted by oneirodynia at 12:26 PM on April 1

This may or not apply to your kitchen or stove, but my sister-in-law had a smell that would come and go without any rational explanation. We smelled it mostly when entering the house from the carport entry but the entire kitchen didn’t have the smell. She finally discovered that the burner controls on the front surface of her gas stove would turn on a fraction of the way if, say, they were bumped as you carried in groceries or similar activities. The smell was more like a spicy smell and not what we associated with the natural gas smell that the city adds to their gas lines.
posted by serendipityrules at 1:25 PM on April 1

I love this question and hope you continue to update us on what you learn. If it were me I’d be just as frustrated as you, and trying every possible investigation. Have you considered logging data? You could capture date, time, location and any observations. Because you mentioned the laundry smell, I also wonder if this is somehow connected to your neighbors. How close are your neighbors? If you are on good terms with them, try to find out if they ever leave their house completely vacant, is the smell still detected? It would be interesting to find out if there is a correlation. Gather all the data you can and it could become a solvable logic problem!
posted by oxisos at 1:48 PM on April 1 [1 favorite]

in that room it comes along with a strong laundry detergent smell- but not the laundry detergent we use

This is a fascinating clue. Now I'm curious about your neighbors' drain pipe situations. But you mention it isn't worse in your basement, though -- is that beneath that room too? All that makes me think it isn't a smell coming up through the floor, and you said you don't smell it outside, so is it safe to assume... the smell is coming from within the house? (Lol)

The other intriguing clue you give is a sump that isn't pumping. Our basement has pipes that run beneath the subfloor and drain to the sump pit that I suppose (?) could conceivably end up with stinky standing water in them. But again, you say the basement isn't the source of the smell so maybe not.
posted by Spokane at 2:14 PM on April 1

You may have seen my previous Ask question about a similar odor, which I recently updated with the successful odor resolution.
posted by samthemander at 2:32 PM on April 1 [3 favorites]

If your house is drafty, could it be something in the neighborhood? Down the end of my street we have a small sewerage pump house and I often feel bad for people who live down there. On really severe days I catch a whiff of sewerage smell even blocks away. Just a thought.
posted by annieb at 5:55 PM on April 1

We had a similar issue at my parents' house when I was in my teens and 20s. The northwest corner of the house would just STINK, mostly when the windows were open, but at other times too. My childhood bedroom was in the thick of it, and I'd have a hard time sleeping in there when I went home to visit.

They finally brought in a professional and found out that when their house was built in 1983, the builders must have used some bad dry wall. The guy took one whiff and was like, "Yup, that's bad dry wall, no question." Not sure why it took 10-15 years to start smelling, but it eventually wore off, though it took a very long time. I know your house is MUCH older than that, but if you had any construction done in the last 50 years or so, apparently materials can turn! My mom is so happy that the house doesn't stink anymore.
posted by leftover_scrabble_rack at 7:35 PM on April 1

If you have carpets and they predate your time in the house, that would be my prime suspect. I have some of those and the odor is more noticeable this time of year because the heat / AC aren't running very much and the odors have a chance to linger without ventilation.

In our case it's dogs and cigarettes but carpets can hold tons of odors and/or literal substances...

Does the smell get worse if you get a section of carpet wet? Or if you bend down and smell the carpet?
posted by mmoncur at 7:45 PM on April 1

Response by poster: No carpets, no drywall (other than in the non-smelling bathroom). Not the stove, which occasionally gets smelly if a pilot light goes out (which happens only every couple of years). I think the next thing I need to do is get up into the attic, and if that yields no info I probably need to keep a smell diary of some sort.
posted by oneirodynia at 9:39 PM on April 1 [1 favorite]

Thinking about what you said about the association with rain... is it about moisture and humidity? Especially damp after a dry spell? Is there bare earth under your house? Thinking about your bedroom, could there have been a spill or something dumped close by?
posted by i_am_joe's_spleen at 10:35 PM on April 1

Does your clothes washing machine have a drip pan under it with a water outflow in case of leaks? If so, that water outflow may be letting sewer gas up unless you fill the p or u trap it has with water (and a bit of bleach) from time to time.

This is a pretty common feature of washer dryers that are above-grade (I.e. not in your basement, instead on an upper floor).
posted by slateyness at 5:29 AM on April 2

Are you on a well with a water treatment system or have a softener in line? On my water treatment system, the back-flush line is piped into the laundry sump. Whenever it regenerates, I can smell the sulfurousness of my well water.
posted by tomierna at 12:45 PM on April 2

Mod note: [btw, this smelly problem and thread has been added to the sidebar and Best Of blog!]
posted by taz (staff) at 5:07 AM on April 8 [2 favorites]