Hi - I Have A Strong Smell Of Smoke A

Hi - I have a strong smell of smoke a lot of the time. No one around me smokes. I smell it a lot in my home where no one smokes. It's so strong sometimes that I think something is burning and I ask my husband to check to make sure nothing is burning. He never smells the smoke when I am having this symptom. I've never smoked and I don't allow anyone to smoke in my house.
What could be causing this sensation?