We're not going to be much help with a generic 'foul smell'. It could be a lot of things. If you think it's your sofa, consider this for a test: get some cheap plastic paint drop cloths and wrap the whole sofa in its own bubble. Seal it with tape. Leave it for a couple days then open it an stick your head in. If it stinks to high heaven, that's your answer.

There are some funky foam, rubber and plastic products coming out of Asia. Just yesterday I used a piece of scientific instrumentation in a plastic road case (like a suitcase) with form fitting dark gray foam inside. It smells like coal tar (or asphalt driveway sealer). Ever been in a Harbor Freight Tools store? Same thing.

Good luck and report back.

I dont think its the couch, the couch is downstairs and smell is confined to the upstairs, i was thinking it could be maybe my ikea furniture, but there wasn't anything where the scent was in my apartment. Its a sourish smell, I cant put my finger on what it smells like. Its not a garbage scent, a litter scent, dog scent, I dont think its a mold, its not musky scent. Thanks for the response, I will try that with some of the things. Do you think it could be ikea furnature?

I got a new wool area rug. It has a peculiar smell, but I think it's finally getting better. I've had it about 2 months.

I know the smell is coming from it, because I never had the smell prior to bringing the rug into the house. Since it's real wool, I assume it's a faint animal-type smell. It was fairly expensive, so I was surprised. When it's been raining outside, the smell is stronger.

I got one of those air purifier/cleaners (a jar of what looks like little gel balls) that you take the lid off of. I set the jar under my china cabinet and it's working.

I have put (unused) coffee grounds in a bowl under furniture to combat odor. You smell the coffee for a little while and once it fades, still no stink...

Did you have the new couch at the first place? If so, is it bonded leather? That stuff can send off horrid smells for a few weeks to months.

Wool has natural oil (lanolin) which does have an odor.

I would certainly suspect new furniture these days. So much of it is made of pressed board, particle board, plastics, foam, stuffing, all of which can emit odors for awhile.

Other things you can use besides coffee grounds: baking soda (which works on acidic chemicals, which your 'sour' smell may be); activated charcoal (the kind you can get for fish tanks is the cheapest way to buy it). Doesn't hurt to try them all.

Do you use gel or rubber insoles in your shoes. I use a heavy pair & then a light weight set on top so easy to wash. Well I washed both sets & the heavy ones drove me out of the house! I took the heavy insoles outside in the sun all day, Sprayed them with Febreze awful smell but they dried finally & not too much smell but would they stink up my shoes if I tried to use them They are about $10 a pr or so. Who knew something to cushion your shoes could stink so much. National brand too! Good Luck but check those shoes sitting there!