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What Is That Strange Smell in the House?

Tony Lawrence was born in 1948 and spent most of his career as a self-employed computer troubleshooter for Unix systems.

What Is That Weird Smell in the House?

When I was very young, we once had a dead mouse in the walls of our home. That's never pleasant, but this mouse, unfortunately, died in the walls of our dining room and, therefore, interfered with family dinners until it had sufficient time to rot away or be eaten by whatever else was in the walls of that old house.

I've looked online and am told that it can take up to two months for that particular smell to dissipate. I don't remember it being that long at all, so it's possible that my father tore into the walls, located the carcass, and restored the use of our dining room in that way. Other sources say that, under the right conditions, the smell might only last a few days, so we also may have been lucky that way.

Given how easily mice can get into our homes, it's surprising that this kind of thing doesn't happen more frequently. Apparently, a small, dead mouse may not even smell enough for us to notice—that's a bit unsettling, isn't it?

A Dead Rat

A rat is much larger than a mouse. A dead rat has a commensurately stronger smell. I am one of the unlucky folks who has experienced this firsthand because of a customer who had a dead rat in the ceiling of his office.

The building where this happened was mostly a food warehouse. I wish I could say that rodents are never found in such places, but of course they are, and it's not necessarily unusual. When these creatures are spotted, exterminators are summoned, and they do their job. Contaminated food is disposed of, and everything returns to normal.

In that sense, I was not particularly surprised to learn that the owner of this company had a dead rat in the ceiling. What did surprise me was that he didn't have it removed.

In retrospect, it may have been because his business, something a grandfather had started many years earlier, was failing rapidly about that time. I had noticed that he seemed depressed, and that actually became serious enough to require hospitalization soon after the rat incident, but at the time, I simply could not imagine how he could sit at his desk with that incredibly foul stench filling the room.

I could not. I gagged and had to leave. I insisted that someone go fetch his computer and bring it to me for diagnosis, and even then, I thought I detected a lingering smell.

That dead rat is in my memory as the worst smell I have ever encountered inside a building.

Strange Smells

Decomposition is pretty easy to identify. Most of us will recognize it instantly, and pinpointing the source usually isn't particularly hard. Getting rid of it might involve inconvenience and expense, but it's not usually mysterious.

Other house smells can be harder to determine. If the smell is persistent, you can probably narrow down the source fairly easily, but if it comes and goes mysteriously, eliminating it becomes much harder. There are some obvious and not so obvious possibilities; if you have a strange smell, perhaps you'll find some help here.

Simple Things

Here are a few simple things that may cause strange smells in your home.

Refrigerator "Science Experiments"

On the small chance that you are a former one-percenter who has now fallen upon hard times and no longer has servants tending to you, I'll mention that a "science experiment" in the refrigerator is surely something even you will figure out quickly enough. What your sheltered life may not have taught you is that your refrigerator has a "drain pan" which can be a source of odors. If that last sentence isn't clear enough, Google "refrigerator drain pan" to learn more.


It's also obvious to all but the most clueless that any sort of wetness from a spill or a careless pet can cause odors to develop in carpets and furniture. Products like Febreze can sometimes fix minor problems like that (it apparently actually "traps" odors, in addition to masking them). If it's really bad, you'll likely have to throw out the carpet or furniture.

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Read More From Dengarden

Damp Clothes

If you don't get to washing soon enough, damp clothes in a laundry hamper can smell. Simple advice for the former multi-millionaire: don't put damp clothes or towels in the hamper. Let them dry on a rack first. I know, your first thought was to just throw them away. We poorer folks don't do that.

Why Does My House Smell Like Cat Pee?

A year or so after moving into our new home, we noticed something that smelled like cat pee. I say "like" because we don't have cats and also because it would come and go, sometimes fairly quickly.

My first thought was that something (mice, birds, bats, squirrels, a raccoon?) had found its way into the attic space. However, we did not hear any scurrying about, and a thorough investigation of the outside and the roof showed no points of entry or any muddy footprints on painted surfaces that might indicate such an invasion.

Of course, critters can also enter from below, but that checked out too. It did not seem to be animals.

I already knew to check the bathtubs. We use our freestanding shower, so both bathtubs can go unused for months. If it goes long enough, the water in the drain trap can evaporate, letting sewer smells into the house.

Smells aren't the only things that can come through a dry drain trap. One of our neighbors was regularly hearing faint voices in their spare bathroom. Those were finding their way through a dry trap also.

The quick fix is to run water, but that wasn't the source of our smell.

The other odd thing about the smell was that it was in two very specific places: in our master bathroom and in the laundry room.


There's another place where sewer smells can find their way into your home.

These are "air admittance valves," sometimes called "Durgo valves." These are supposed to be trouble free and extremely long lasting, certified for up to 30 years of use according to Wikipedia.

As these are relatively inexpensive and fairly easy to replace, we tried that. The smells stopped.

Rotting Wood

When my mother became too old to live alone, we converted our attached garage into a living space for her. She had her own bathroom, bedroom, and living room, her own heat and thermostat. It was a nice "mother-in-law apartment."

After ten years, she had to enter a nursing home, and that part of the house was mostly unused for another decade. As we were preparing our home for sale, we noticed that there was a musty smell in the area of what had been her closet.

We tried the usual things—Febreze, running dehumidifiers, turning up the heat higher to dry things out more, and so on, but the smell lingered. In fact, it seemed to be getting stronger.

Being anxious to get our home on the market (this was just as the housing bubble started its collapse), we even had an expensive "Humidex" system installed. That didn't help either.

It was contractors re-shingling the outside of the garage who found the real culprit: a rotting wood sill. This was definitely the fault of the original contractor who had done the garage conversion, as it was their shingles we were replacing. They had installed no vapor barrier at all!

After twenty years, it was far too late to go after them for the cost of replacing that, but the discovery of their carelessness did make me angry. We stripped ALL the shingles, checked for other rot, installed a proper barrier and a new sill, and put new shingles back. That was fairly expensive also, but the smell was vanquished.

Formaldehyde and Other New Home Smells

Our new home had other odors. This is a manufactured home, and the literature we were given about it plainly stated that some materials contain formaldehyde. You can smell this, and some people have a reaction to it.

One of the strongest places we noticed that was in our bedroom closets, so we painted all those surfaces with a sealing polyurethane paint. I'm not sure that actually accomplished anything useful. However, over time formaldehyde outgassing diminishes and eventually stops.

Anything Else?

Also, the sink overflow drains can smell—clean them with a half cup of baking soda mixed with a tablespoon of salt. Pour that in the overflow drains and then add vinegar several times—it will foam out. Finish flushing with water.

Finally, we’ve had dead mice inside the walls of the whirlpool tub. It has panels where you can get in, and while in there, hopefully seal up where they get in.

If you've tracked down a strange household odor, I'd love to hear about it in the comments.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

Questions & Answers

Question: What does rotten wood, such as a wooden sill plate, smell like?

Answer: Like wet wood, but more pungent and unpleasant.


Tony Lawrence (author) from SE MA on February 14, 2019:

Sorry, Joanna, I have no idea.

Joanna from Atlanta on February 12, 2019:

Tony, can you give me an alternative to rotten wood? This smells more like vegetation, something akin to the dumpster in our complex, but less pungent. Is there any place you can direct me, to further my investigation, or will cutting a hole in the closet drywall expose all I need to see? I am not convinced that it is merely rotting wood, there is something much stinkier going on here.

Tony Lawrence (author) from SE MA on February 12, 2019:

I suppose the smell could move with the wind and heating. Going to be hard to convince the landlord of that.

Joanna from Atlanta on February 12, 2019:

I’ve had a couple of the maintenance ppl in, one of which came in from the leasing office, all proclaiming its food being cooked. I have no problem with cooked food smells, but this is not one of them. Would rotten wood move around, like a ghost smell? Could it have mold in it? Rotting wood wouldn’t smell that strong, would it? I am one of those unfortunate ppl that get migraines from time to time, & this odor sets one off. This has been a weekly occurrence if not more.

Tony Lawrence (author) from SE MA on February 12, 2019:

Sounds like rotting wood to me, Joannabrit.

Joanna from Atlanta on February 11, 2019:

Pls help me Identify this rotten, acrid pungent smell of rotten onions mixed with cabbage & something overly sour underlying the rest. It comes and goes, is evident more in the evening & on a Sunday. It starts in laundry room sometimes, or the master. Closet. The hall and bathroom. But all along that back wall. We cannot pinpoint it & it’s an apt. Built in the ‘50’s complex do nothing to help. We are going to leave. This is been going on for a year. When first moved in, before they cleaned up and painted, I came in took photos. There was black mold behind tile in shower, and cupboards. They painted over it and put tile over the rest. Pls help

Jasper175 on January 16, 2018:

No one can identify the smell in my apt!!! Making me crazy.

I ruled out:

Rancid grease build up

Dirty floor boards


Dirty Walls

Soiled couches, drapes, carpet

Old food

It permeates primarily in the living room. But throughout the whole upstairs which is the main level.

I do know squirrels live in the above apartment gabel ... But I don't know what squirrel urine or feces smells like. Let alone there should be a plate barrier between me and upstairs and the Attic Gable area.

I don't know

Emily Tack from USA on March 15, 2015:

Oh, I am very familiar with the smell of rotting fruit rats that died in our attic. We live in FL, so it was very interesting living with that rancid overpowering odor, until we were able to eliminate the sources. For some unknown reason, a lot of little fruit rats decided our attic was "the place to be". They were "trap-smart", so we eventually reluctantly resorted to poison. We evidently had quite a few, as they devoured 5 large pans of it, 5 days in a row. Thereafter, we did not see any more of them running around outside.

You are right - the smell is unmistakeable, and quite foul.

Tony Lawrence (author) from SE MA on February 01, 2012:

Hadn't heard of Air-Renu, thank you!

Matt Ringer on February 01, 2012:

I just moved and the previous tenant had pets and also smoked the odors were throughout the house. The landlord compensated me for repainting all the interior walls I added the Air-ReNu paint additive that a friend recommended and thankfully, the house stays smelling fresh no more odors

Tony Lawrence (author) from SE MA on January 31, 2012:

I can't imagine three boys.. good luck!

hawkdad73 from Riverside, Iowa on January 31, 2012:

I agree. The smell of decomposition is unmistakeable. Unfortunately, a lot of the smells you mentioned in your Hub are too.

Three boys are unfortunately making moisture a common culprit in more ways than one. For example, our bathroom smell fluctuated from that of a locker room and public restroom Fortunately, thanks to antiseptic wipes, frequent deep cleanings are not necessary.

Useful hub. Thanks

Tony Lawrence (author) from SE MA on January 30, 2012:

Garages are especially hard to keep mouse free. The same general advice applies - seal, seal, seal, but it is never easy.

Gloria from France on January 30, 2012:

Good hub with a lot of good information. We have had the odd mouse in the garage but not the smell thank goodness.

I am going to bookmark this just in case.

voted up

Tony Lawrence (author) from SE MA on January 29, 2012:

Ahh, yes: you can't just ameliorate it temporarily. That you have to fix.

Ken Kline from USA on January 29, 2012:

Homes with smell have a terrible time selling. Sometimes it is the unseen. Enjoy this article very much.

In my travails with our vintage home my wife has made me open charcoal in the basement. Yes, the lighter fluid kind for the Weber grill. It has does wonders for the musty smell but ah, the read problem is my next job - removing the moisture and making sure the moisture problem really is "cured".

Excellent! Voted up!!!!

Tony Lawrence (author) from SE MA on January 28, 2012:

Thanks for the SCOE tip!

Leah Helensdottr from Colorado on January 28, 2012:

I had a cat who became ill and stopped using her litter box. Cat urine is one of the hardest odors to get out of carpet, but after unsuccessfully trying several products (including, on one exasperated occasion, pouring bleach on a hidden area of the carpet), I found one that really works: Super Concentrated Odor Eliminator (google SCOE). Follow the instructions carefully and don't bother spraying if the urine is in the carpet--pour it on and saturate the affected area. It's like a miracle; the odor vanishes within a minute or two. I'm glad to pass on this helpful tip to other people who are dealing with dog or cat urine odors.

Another good hub, PC; I voted it up and useful.

Tony Lawrence (author) from SE MA on January 28, 2012:

Not good for customers..

Peggy Woods from Houston, Texas on January 28, 2012:

My parents once had a rotting animal smell in their Real Estate office which was located next to a garden nursery. Whew! What an terrible smell! Not the best place for that to have happened as you might well imagine.

We have also had the experience of a sewer smell coming into the house from a faucet that we rarely used. Now I make sure and run water through them on occasion to keep that water well filled.

Excellent hub with good tips! Up and useful votes.

Tony Lawrence (author) from SE MA on January 28, 2012:

Yes, if you have ever smelled it, you don't forget it.

Sandi from Greenfield, Wisconsin on January 28, 2012:

What an interesting article! I really learned a lot and I appreciate you sharing all this information. I too have had the "dead mouse" smell in my house (recognized the smell from the unfortunate ones I actually saw dead in their cage)but never could find the source before it dissipated on its own. Voted up and useful.

Tony Lawrence (author) from SE MA on January 28, 2012:

Could have been a mouse..

Kris Heeter from Indiana on January 28, 2012:

I had one of these now so lovely smells a few weeks ago in my business. I was pretty sure it was a little dead mouse but couldn't find it - thankfully after about 5 days ago it slowly went away.

Tony Lawrence (author) from SE MA on January 28, 2012:

@Wes: Maybe you should do a hub?

@Trish_M - I figured that if I learned something (those AAV's) there might be things others don't yet know about. I couldn't find one page that said everything I knew, so I wrote it :)

Wesman Todd Shaw from Kaufman, Texas on January 28, 2012:

Oh man - the awful smell in the church I grew up in after someone had put out poison...WHEW!

It's a pretty big building, and has those ceiling tiles marking the bottom of the sub ceiling and the beginning of the space where air handlers and plumbing pipes and electrical wires live......but after not much time you can see from below where the dead rat or mouse is, as the decomposition ...changes the colour of the white tile.


First ever full time and benefits galore job I had was as a ..."filter tech" at the Dallas Independent Schools (there's LOTS of schools and buildings)...and as the guy who drove one of the box trucks full of air filters around, I also got to be in charge of odour odours.

I can't recall what the stuff was called, but I'd just mist it on some new air filters, and soon the entire school would smell better. The "stuff" was very strong, and you wouldn't want to get it onto your skin either.

Often in schools - I had too many of them and they were too big - nobody considered finding a dead mouse, just over coming the odour. Skyline High in Dallas has seven three story buildings, and who knows how many two story and single story buildings...then ...maybe a hundred portable buildings and several miles of tunnels for maintenance underneath it all.

Except for when it's a hundred and ten degrees outside and my air conditioner simply can not keep up - I'm proud to live in my tiny travel trailer where there's nowhere for a mouse to die without me knowing about it. Heck, never seen one in or around here.

I should quit, I could easily type another thousand words of mouse story's here this morning.


Tricia Mason from The English Midlands on January 28, 2012:

Hi :)

This is a very entertaining ~ and potentially very useful ~ article :)

Tony Lawrence (author) from SE MA on January 28, 2012:

Yeah, mice are not fun. The secret is sealing them out:

mljdgulley354 on January 28, 2012:

pcunix I just posted a mouse story. I don't remember having a smell before being confronted with that critter but I have been in homes with the mouse smell and it can be very overcoming. I did have the refrigerater pan problem and it cost me a bundle to learn about that one since I had to hire a repairman to find it. Enjoyed reading and learned a few things from this hub that I will be checking out in my home.

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