In addition to conversion unit fundamentals, inefficient operations can send light end
molecules into the fuel system. For example, poor use of hydrogen can lead to hydrogen
letdown into the fuel system. Furthermore, refineries often have a greater fuel gas
containment problem in the hot summer months when higher volumes of C3+ material
make their way to the fuel system. This can be due to poor cooling tower operations
where summertime cooling water supply temperatures are as high as 90 °F.