Although I agree with @johnbishop you should contact your physician as these phantom smells may potentially be serious. I always look at symptoms from an Epilepsy point of view since that is my mimesis. Temporal Lobe Epilepsy is a possibility although slim in my opinion. In TLE Epilepsy odd odors usually last 30 seconds to a couple minutes. It doesn’t sound like Focal Non-Convulsive Status Epilepticus in this layman’s opinion. But whatever it is has the potential of being serious. Please contact your Physician.