How can I find the source of a mysterious bad smell?

Question

We have recently moved home, and all is fine appart from a mystery smell which I'm unable to track down. It's driving me crazy (actually, my wife thinks I am crazy as she can't smell it). I'm hoping someone on here could offer some tips on how to track it down, or what it might be. Here's some info:

Background: The house is a two floor (plus basement) block/concrete construction. There is a wide hallway on the groundfloor connecting the rooms (including kitchen, toilet/shower room, stairwell). The stairs are wood-board on concrete. The floor in the hall and kitchen is tiles over concrete, the rest woodblock/parquet over concrete.

Location of the smell: I usually smell it when coming down the stairs, seems to be strongest about half way down. However sometimes it doesn't smell on the stairs at all, but rather in the ground floor hallway. Seems to move around quite a lot. Occasionally I have felt it upstairs, but assume this is it drifting. The basement smells fine.

The Smell: The best description of the smell I can give is something like old rubbish.

What I've investigated so far:

1) Something died somewhere? This was my initial thought, and since I usually notice the smell on the stairs I thought I'd try there first. I've taken up some of the wood on the stairs (not all yet) but not looking promising, as there really isn't much space between the wood boards and the concrete. Not really sure where else something could have gotten, as everything seems to be tight against the concrete.

2) Smell from kitchen moving into rest of house? I never really detected a bad smell in the kitchen, but thought I'd rule it out anyway. I thought maybe it was the bin under the kitchen sink that might be causing it. So I moved the bin to a small storage room at the back of the kitchen (and kept the door closed) and thoroughly cleaned inside the cupboard under the sink. No change. I also looked behind all of the cabinets for a problem, but could not see anything.

3) Gas from drains? The sink doesn't smell in the kitchen, and it's got a P-bend trap on the pipe - so I can't see a problem there. Cant detect a smell from the plugholes in the bathroom either. The bathroom sink waste pipe has a bottle-trap on it. Don't know if there is a trap on the shower as it's a sealed unit, but I'm guessing yes (and can't smell anything).

Can any one think of something I might have missed, or give any advice?

Answer 1

Guesses so far...

• Stinky mop.
  • Solution: Wash the mop.
• Stinky Jack Russell Terrier.
  • Solution: Wash the dog.
• Dead thing in wall.
  • Solution: Find the dead thing and remove it.
• Dead thing in vent.
  • Solution: See above item.
• Stinky toilet.
  • Solution 1: Flush the toilet.
  • Solution 2: Wash the toilet.
  • Solution 3: Replace wax ring.
  • Solution 4: Light a match / candle.
• Gas leak.
  • Solution: Call gas company to find and fix leak.
• Stinky ghost.
  • Solution 1: Wash the ghost.
  • Solution 2: Exorcism.

Answer 2

It took us 4 months to track down our odor. It was ghostly, in that you would only catch a small whiff once in a while while in the house; however, when you came back into the house after being out just a few hours it smelled much worse. It was mostly isolate to the kitchen, but, again, you could smell it at the front door when coming in from outside. To make a 4 month story short, it was rancid grease on top of the kitchen cabinets. No one had cleaned up there in 15 years. The original owners, who built it, had also put support frames up there for displaying things, and those were not painted; so they absorbed all the odors. 3 years later, after cleaning up there thoroughly, removing the frames, and sealing the tops of the cabinets, we have no smell; but ti did linger for about a year, through quarterly washings of the tops of the cabinets. The good news is the seller took a very big hit on the price for that odor.

Answer 3

Get a UV light that detects pet stains in the dark. It also detects a few other stains, you may find the source with that.

Answer 4

If the house is old enough, the kitchen sink probably drains into a catch basin. It will smell unless it has an air-tight cover, especially if you use a garbage disposal.

It may be time to honey-dip the sump (pump) and/or the catch basin.

Leaky sewer pipes underneath the slab can sometimes smell like 'old garbage' (opposed to the new kind) as stuff builds-up outside the pipe. I've stop-gaped this problem by caulking where the slab meets the walls and installing a radon fan on top of the stack to keep a negative pressure on the system. We're still looking into replacing the main run that has been somewhat crushed by the walls, as the building settled. ($$$, not DiY)

Answer 5

Check if there's something inside or behind electric radiators, if you have these. A classic but terrible prank is to put shrimp shells inside a heating radiator, very hard to find out.

The smell seems to move because of slow air movements (and is probably pulled to the stair because the air rises or falls between your two floors, think about if the smell is in cold air going downwards or hot air moving upwards. You could also try to isolate it by taping the sides of the doors (without anyone locked up inside, of course).

Answer 6

We spent ten years with a mysteriously stinky basement. We just decided "it's an old house, that's how our basement smells." Upon selling the house, the buyer's inspector noticed we had an uncapped cleanout in our sewer line. It was just letting sewer gas flow unchecked into our basement.

We put in a plug and the entire house – especially the basement – smells like ten times better.

Of course, we've sold the place so mostly the new owners will get to enjoy the non-stinky house.