What is pressure refueling and how does it work?
With a pressure fueling system, rather than fueling through holes in the tops of the wings, a fuel truck or fuel hydrant is used to push fuel into the airplane through a fitting at about 50 psi. The fuel fitting is generally in the right wing. A fueling control panel allows the fueler to fill the tanks to the amount called out by the flight plan.
These large aircraft still have an overwing fueling port for those times when the pressure fueling system is inoperative.
There is nothing to prevent fuel vapors from escaping to atmosphere.
I'm an Air Force fuel systems supervisor.
Yes...air is pushed out of the tank vents during fueling operations, but there are no flammable vapors in jet fuel until the fuel temperature exceeds at least 100 deg. F. There is odor, but not dangerous vapors until that temperature is reached.
The single point system is primarily necessary to reduce spills...it's a closed system that allows faster fueling with less environmental impact.