We live in a 3 level duplex. We have a sweaty smell that comes and goes. We do not notice it in the basement(small basement w/furnice & water heater only). We also do not notice it upstairs(2 bedrooms & bathroom). We notice it inside near the front door & a little on the stairs leading to the top floor. The main floor we notice it in the livingroom and dining room most strong. Nothing in the kitchen or lalundry/half bath. It is not connected to weather, heating blowing. We have checked carpet, furniture, etc. Sometimes we won't notice it for months & then it will be back for months. This time it started, strange as it sounds, with a smell like pencil shaving (freshly sharpened pencil) & then became the sweat smell over a day or 2. Thanks for any help.

Do you have access to all rooms in the house? if not, it may be from a room you can't get too. A Renter?

Is there just the one furnace for all 3 floors? If so you do share all the same air so Stratmando is likely on to something

We can get to all rooms, but only notice the smell in dining & living rooms. Furnace in basement is used to heat our 3 floors. Other half of duplex has different furnace. We do rent so who knows whatthe duct work is like.

Carpet or something under the couch?

New carpet 1 year ago. Had smell before & after. Tried to smell carpet, furniture, pillows, even walls & around windows, no luck. Today we don't even smell it, but yesterday it was very strong. We will keep searching...