You can smell cigarette smoke even when there is no actual smoke present due to a condition called phantosmia, or olfactory hallucinations. Phantosmia causes you to perceive smells that aren't really in your environment. Cigarette smoke is a common phantom odor reported by many people with this condition. Phantosmia can arise from various causes ranging from common and non-serious ones like colds, allergies, sinus infections, or exposure to certain substances, to more serious conditions like migraines, nasal polyps, or neurological issues including stroke, brain tumors, or diseases such as Parkinson's. It can also appear after respiratory infections like COVID-19. Sometimes medications or mental health disorders contribute to these phantom smells. Importantly, phantom smells may also be idiopathic, meaning the cause is unknown. It's also possible that lingering real odors on clothes, furniture, or air ducts might trigger the sensation even after the actual source is gone. In cases where the phantom smell is persistent or concerning, it’s wise to consult a healthcare professional to rule out serious underlying conditions or to receive appropriate treatment. In summary, smelling cigarette smoke without an actual source often results from phantosmia caused by sinus, neurological, or environmental factors, and occasionally more serious health issues.