As I'm reading "Ignition!" I'm finding one point baffling: vapor pressure being such a big deal. Outgassing of both fuels and oxidizers would cause dangerous pressure build-up. The book describes the hair-raising stress of handling materials that release oxygen. The utter horror of watching technicians estimate the pressure by measuring barrel bulging. The stringent requirement for periodic manual venting. Abandoning one promising line of research purely due to unacceptable vapor pressure.
A check valve is a really simple, cheap, small device that would neatly protect the contents of the container from environment, while allowing whatever accumulates in the container to vent once the pressure inside rises above a preset value. Even equipping individual barrels with these would cost pennies. Did no-one think of that, or is there some other reason making this impossible or impractical to such a degree that vapor pressure would become an insurmountable problem?