.....but I do smell mold/mildew and fried wiring.
I agree with time2go, that for the most of you this is sinus related. I am not a doctor, but have had sinus issues ever since I had an abscessed tooth that caused a sinus infection - and a mean migraine - that was about 16 years ago.
For years, on and off, I would smell mold/mildew, or fried wiring at random times. It would usually pass in a few minutes to a few hours. About six months ago, I started bicycling to work, and started to notice that when I did, I would get a bad mold/mildew smell in my nose - especially after I jumped into a steamy shower. It started to concern me, so I have spent all evening on the web - which led me here.
I suppose I don't smell smoke so much, because I smoke. However, there are times when I am at work, where no one smokes, that I smell it - but not when I have been smoking. I can't attribute it to my sinuses, but it really fits in with what the rest of you say.
Some observations I have made; most everyone that has posted, has some sort of sinus issue or symptom. Scratchy eyes and throat, bad tastes, ear problems, headaches/migraines, congestion, tinnitus, and nausea/vomiting can all be associated with the sinuses. The problems for the most part appear to come from allergies, sinus polyps, injury, and medications.
My remedies are none. Sometimes a neti pot works for me, but due to my inconsistency, I have no advice - it is cheap and may work. As far as sinus headaches, the only two things that work for me are sudafed and alcohol - but that doesn't help the smell.
Goodnight all, the sinus headache is starting - which tend to be in the evening, otherwise they really get bad. At least the smell is going away - for now.