Fuel vapors refer to the evaporated form of a fuel, such as gasoline or diesel. When fuel evaporates, it turns into gas and creates vapors. These vapors can be flammable and are often released when we pump gas or use other fuel-powered devices.
The gas pumps at the fuel station have automatic sensors on them (for safety reasons) that shut off automatically when too much fuel vapor is present. (yourmechanic.com)