Why am i smelling gas or diesel type smell all the time?

Nasal disease : If you are having this gas smell all the time and there is no such chemical in your environment, then you may have a disease in the area of smell fibers located in the front part of the brain and upper nasal passageway. Cacosmia is the name of this problem.. If it persists you need to see a specialist such as an ENT or neurologist to have imaging studies to rule out more serious conditions.