i am sorry but there isn't any way around my answering this question without injecting some medical terms into the discussion. the sense of smell is referred to in medical terminology as the olfactory system. what you are describing in your question is called olfactory hallucinations. in the medical community the technical name for olfactory hallucinations is called "phantosmia" (probably derived from phantom). phantosmia can present itself in a very real manner. suffers smell an odor like smoke (or some other odor) and may even experience a gaging sensation. in actually there is really no smoke or environmental cause supporting that reaction. phantosmia can be caused by some serious medical conditions that require discussion and investigation with a doctor. these may include brain damage caused by tumors or trauma epilepsy and infectious damage to the olfactory. system.
why do i smell smoke and there is no smoke