system
Given the following post, respond as if you're commenting on Reddit:
human
Why can't you refuel while the engine is running?

I know this 'rule' in the context of cars, but I assume also true for airplanes and boats. Why is this the case? Its not like refuelling opens the combustion chamber... And if fumes are the ones in danger to ignite, couldn't that happen from the petrol in the tank anyway? Excuse my poor knowledge of internal combustion engines !

Edit: Thanks for all the answers. To simplify, I will make a clarification before going to sleep; for a car in a gas station, what would cause ignition? The electrical wiring? The buildup of static charge? The heat in the engine components? Or the engine's combusting? ... For a brand new car what would be the main danger, and how has this changed over the years i.e. by using different materials / engine design?
gpt
Generally there is no issue with refueling on modern cars while it is running. The only issue is the EVAP system can test while you are refueling. The EVAP system monitors and controls the capture and burning of fuel vapors in the tank. Gasoline is always creating vapors and those vapors are stored and burned when the engine is running under certain conditions. This system is also why you should not top off as liquid fuel can damage the components. The test is to verify the system is sealed so no vapors are leaking into the atmosphere. If it runs while you are refueling it will set a code and turn your check engine light on. Then you have to go get it cleared if you know that is what caused it or pay to have someone try to diagnose a “ghost” concern.