What Is That Strange 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 on-line 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 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 first hand 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.
Decomposition is pretty easy to identify. Most of us wil recognize that rather 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.
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 for "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.
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.
Cat pee smell
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 were not hearing 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 that Wikipedia article linked above.
As these are relatively inexpensive and fairly easy to replace, we tried that. The smells stopped.
When my mother became too old to live alone, we converted our attached garage into 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.
Exterior paint should never be used indoors. I've never had that problem, but if you do, you are going to need to fix it - breathing those fumes is not good.
If you've tracked down a strange household odor, I'd love to hear about it in the comments.
Questions & Answers
What does rotten wood, such as a wooden sill plate, smell like?
Like wet wood, but more pungent and unpleasant.Helpful 7