Hello, just wanted to chime in with my experience with phantom cigarette smoke. I'm a non-smoker.Smoked briefly 20+yrs ago. Started smelling very distinct cigarette smoke in July 2020 randomly in my 6mo old house that had never been smoked in. It started strong. After a week of constant smelling I made appt. with a very good ENT. He first suspected I had inhaled mold and had a sinus infection. Put me on antibiotic which did nothing.Next ordered a CT scan of sinus,which showed chronic sinusitis which he said was not relevant. Next was an MRI of the brain looking for a tumor,focusing on olfactory. This showed normal. He then suspected it might be an early sign of dementia / Alzheimers. He ordered a hearing test which show some loss that may be dementia related. By this time several months had passed and the smell slowly diminished and them went away completely. Then reappeared as strong as ever 3 days ago while sitting at home. The smell is now noticeable when I'm outside of my home,which wasn't the case before.I'm going to try to get an order for an MRI scan specifically for Alzheimers as I do have a very strong family history. I'm 54 yo male.