On July 16, 1934 Dr. Kurt Wahmke and three technicians were mixing 90% H2O2 and Ethanol in a steel tank at Kummersdorf, Germany. The tank was connected to the combustion chamber of a rocket engine with a single valve between, no flame non-return finger was used. Dr. Wahmke was obsessed of the question if the use of a fuel/oxidizer mixture prior ignition would be dangerous.
The resulting explosion after ignition killed Dr. Wahmke and two of the technicians. They were the first and only deaths of technicians of German rocket development during the Second World War.
So I should be reminded how dangerous it is to mix fuel and oxidizer prior ignition in a single tank. I will use one tank for the liquefied fuel and a second one for the oxidizer.